Allen-Bradley Absolute Encoder Module User Manual

AllenĆBradley

Absolute Encoder

Module

(Cat. No. 1771-DE)

User

Manual

Table of Contents

Using This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter Objectives

What This Manual Contains

Audience

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Warnings and Cautions

Summary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1Ć1

1Ć1

1Ć1

1Ć1

1Ć2

1Ć2

Introducing the Absolute Encoder Module . . . . . . . . . . . . .

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Example Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Module Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Compatible Processors

Compatible Encoders

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

State of Outputs Upon Loss of Input Power

Module Description

. . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Electrostatic Discharge

Specifications

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2Ć1

2Ć1

2Ć1

2Ć1

2Ć2

2Ć2

2Ć2

2Ć3

2Ć5

2Ć6

2Ć7

Configuring and Installing Your Module . . . . . . . . . . . . . . .

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Electrostatic Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Setting Configuration Plugs

Response to External Fault

Keying

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power Requirements

WiringĆArm Connections

Installing the Module

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3Ć1

3Ć1

3Ć1

3Ć1

3Ć4

3Ć4

3Ć5

3Ć8

3Ć11

Module/Processor Communication . . . . . . . . . . . . . . . . . .

Chapter Objectives

Block Transfer

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BlockĆtransferĆwrite Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

WriteĆData Throughput Time

BlockĆtransferĆread Data

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Programming Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Programming Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . .

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4Ć1

4Ć1

4Ć1

4Ć1

4Ć4

4Ć4

4Ć5

4Ć7

4Ć7

ii

Table of Contents

Offset Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Offset Feature

Offset Words

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Programming Considerations with Offset . . . . . . . . . . . . . . . . . . .

5Ć1

5Ć1

5Ć2

5Ć6

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Causes of BlockĆtransfer Errors . . . . . . . . . . . . . . . . . . . . . . . . . .

Errors Indicated by Diagnostic Bits . . . . . . . . . . . . . . . . . . . . . . .

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BlockĆtransfer Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BlockĆtransfer Timing for PLCĆ2 Family Processors . . . . . . . . . . . .

BlockĆtransfer Timing for PLCĆ3 Family Processors

Application Considerations

. . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Application Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6Ć1

6Ć1

6Ć1

6Ć2

6Ć2

AĆ1

AĆ1

AĆ8

BĆ1

BĆ1

BlockĆtransfer Ladder Diagram Examples . . . . . . . . . . . . .

Bidirectional BlockĆtransfer for PLCĆ2 Family Processors

Bidirectional BlockĆtransfer for PLCĆ3 Processors

. . . . . . . .

. . . . . . . . . . . . .

ReadĆonly BlockĆtransfer for PLCĆ2 Family Processors . . . . . . . . .

CĆ1

CĆ1

CĆ4

CĆ6

Bit and Word Descriptions of Block-transfer Data . . . . . . .

Block-transfer-write Data

Block-transfer-read Data

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DĆ1

DĆ1

DĆ2

Connection Diagrams for AllenĆBradley Encoders . . . . . .

Connection Diagrams for AllenĆBradley Encoders . . . . . . . . . . . . .

0 to 359Ćcount, 10Ćbit, BCD, SingleĆended Output . . . . . . . . . . . . .

0 to 255Ćcount, 8Ćbit, Standard Gray, SingleĆended Output . . . . . . .

0 to 359Ćcount, 10Ćbit, BCD, SingleĆended Output, Latching . . . . . .

EĆ1

EĆ1

EĆ1

EĆ3

EĆ4

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FĆ1

Using This Manual

Chapter

1

Chapter Objectives

Read this chapter to familiarize yourself with this manual. It tells you how to use the manual properly and efficiently.

What This Manual Contains

This manual contains 5 chapters and 6 appendices:

B

C

E

F

5

6

A

Chapter/

Appendix

1

2

Title

3

4

D

What's Covered

Using This Manual

Introducing the Absolute

Encoder Module

Configuring and Installing

Your Module

Module/Processor

Communication

Offset Feature

Manual's purpose, audience, and contents

Module description, features, and hardware components

Feature selection and installation procedures

Troubleshooting Troubleshooting guide

Block-transfer Timing Instructions for determining blockĆtransfer timing

Application Consideration Encoder shaft speed

Block-transfer Ladder

Diagram Examples

Biat and Word Description of Block-transfer Data

Glossary

Words and file parameters of blockĆtransfer data

Programming to compensate for shaft offset

Examples of blockĆtransfer programming

Details of blockĆtransfer file data

Index

Audience

In this manual we assume that you know how to:

program and operate an Allen-Bradley programmable controller

program block-transfer instructions

1Ć1

Chapter 1

Using This Manual

Warnings and Cautions

Summary

If you do not know how to do either of these, read the user’s manual of your processor. Refer to our Publications Index (publication SD499) for a complete list of publications.

Throughout this manual we include special notes to alert you to possible injury to personnel or damage to equipment under specific circumstances.

WARNING: tells you when people may be injured if procedures are not followed properly.

CAUTION: tells you when machinery may be damaged if procedures are not followed properly.

This chapter told you how to use this manual efficiently. The next chapter introduces you to the absolute encoder module.

1Ć2

Chapter

2

Introducing the Absolute Encoder Module

Chapter Objectives

Example Applications

Module Functions

This chapter describes:

example applications of the absolute encoder module

functions of the module

Allen-Bradley processors compatible with the absolute encoder module

encoders you can use with the module

module specifications

The absolute encoder module is usually used for:

absolute-position feedback

high-speed response to position based on encoder values

immunity to loss of position from power loss or power interruptions

The Absolute Encoder Module (cat. no. 1771-DE) is an intelligent module that provides high-speed response to machine position independently of the programmable controller scan. It can:

monitor the position of an absolute encoder that has up to 12 bits

control up to eight high-current outputs based on comparisons between encoder position and your preset values

provide throughput for all eight outputs in less than 200 us

communicate with the programmable controller through block transfers

return the status of outputs and the position of an absolute encoder to the programmable controller

In addition, the module can switch 2A DC per output with no derating when all outputs are on, allowing 16A continuous per module.

2Ć1

Chapter 2

Introducing the Absolute Encoder Module

Compatible Processors

You can use the absolute encoder module with any Allen-Bradley programmable controller that uses block-transfer programming in both local and remote 1771 I/O systems. Processors that are compatible with the module include:

Mini PLC-2 (cat. no. 1772-LN3)

PLC-2/20 (cat. no. 1772-LP1, -LP2)

PLC-2/30 (cat. no. 1772-LP3)

PLC-3 (cat. no. 1775-L1, -L2)

Mini-PLC-2/15 (cat. no. 1772-LV)

Mini-PLC-2/05 (cat. no. 1772-LS, -LSP)

Compatible Encoders

You can use Allen-Bradley absolute encoders that use up to 12 bits with the absolute encoder module. Allen-Bradley encoders with the following bulletin numbers are compatible with the absolute encoder module:

Bulletin 845A

Bulletin 845B

Bulletin 845C

The module is also compatible with absolute encoders that have the following specifications:

single-ended or differential encoder output signals

TTL-compatibility (output drivers)

capability of sinking 11mA (single-ended) or 18mA (differential) per channel

BCD, natural binary, or standard Gray code format

State of Outputs Upon Loss of

Input Power

You can select the state in which the outputs will be if the module loses input power. A configuration plug on the right printed-circuit board allows the outputs to:

turn off

remain in their state at loss of input power

2Ć2

Module Description

Chapter 2

Introducing the Absolute Encoder Module

The next four sections give a description and specifications of the absolute encoder module.

Status Indicators

The module has 10 LED status indicators (Figure 2.1):

Eight output status indicators (one for each output) light when the corresponding output circuitry is energized.

One green ACTIVE indicator lights when the module is powered and functioning.

One red FAULT indicator lights when the module detects a fault and momentarily lights at power-up.

Figure 2.1

Status Indicators

ABSOLUTE

MODULE

Status Indicators

3

4

1

2

Active

0

6

7

Fault

Output Fuses

The module has eight 3A rectifier fuses (one per output) located on the right printed-circuit board. Figure 2.2 shows the fuse locations.

2Ć3

Chapter 2

Introducing the Absolute Encoder Module

Figure 2.2

Fuse Locations

F1 F2

F3 F4

F5 F6

F7 F8

Right Board

13303

Terminal Identification

Figure 2.3 identifies each terminal of the absolute encoder module. The bit x/common terminals refer to:

not bit x terminals (uses with differential output encoders) or

common terminals (used with single-ended output encoders)

2Ć4

Chapter 2

Introducing the Absolute Encoder Module

Electrostatic Discharge

Figure 2.3

Terminal Identification

Left

Wiring

Arm

Bit 0

Bit 0 / Common

Bit 1

Bit 1 / Common

Bit 2

Bit 2 / Common

Bit 3

Bit 3 / Common

Bit 4

Bit 4 / Common

Bit 5

Bit 5 / Common

Bit 6

Bit 6 / Common

Bit 7

Bit 7 / Common

Bit 8

Bit 8 / Common

Bit 9

Bit 9 / Common

Input Supply

(+5V dc)

15

16

17

12

13

14

20

21

18

19

9

10

11

6

7

8

3

4

5

1

2

Right

Wiring

Arm

15

16

17

12

13

14

20

21

18

19

9

10

11

6

7

8

3

4

5

1

2

Output Supply (+5 to 24V dc)

Output 0

Output 1

Output 2

Output 3

Output Common (+5 to 24V dc)

Output Common (+5 to 24V dc)

Not Used

Output Supply (+5 to 24V dc)

Output 4

Output 5

Output 6

Output 7

Output Common (+5 to 24V dc)

Output Common (+5 to 24V dc)

Not Used

Bit 10

Bit 10 / Common

Bit 11

Bit 11 / Common

Input Common (+5V dc)

For Outputs

0 - 3

For Outputs

4 - 7

12832

Electrostatic discharge can damage integrated circuits or semiconductors in this module if you touch backplane connector pins. It can also damage the module when you set configuration plugs or switches inside the module. Avoid electrostatic discharge by observing the following precautions:

Touch a grounded object to discharge yourself before handling the module.

Do not touch the backplane connector or connector pins.

When you configure and replace internal components, do not touch other circuit components inside the module. If available, use a static-safe workstation.

When not in use, keep the module in its static-shield bag.

2Ć5

Chapter 2

Introducing the Absolute Encoder Module

Specifications

CAUTION: Electrostatic discharge can degrade performance or damage the module. Handle as stated above.

Module Location

Any 1771ĆI/O chassis; any 2Ćslot I.O group

Input Power Supply

+5V DC +0.25V (total output

voltage tolerance includes line

regulation, load regulation, drift,

and ripple)

Current Requirement

300mA (maximum)

Number of Inputs

Up to 12 encoder input bits per

module

Encoder Formats

BCD

Natural binary

Standard Gray

Digital Resolution

Up to one part in 4,095 with natural binary and standard

Gray encoders

Up to one part in 999 with

BCD encoders

HighĆtrue Logic

From totem pole, open collector, or differential line drivers

Can select direction of rotation of increasing position for Gray code encoders

Input Voltage Range and Logic State

Logic 1: 1.7V DC

Logic 0:0.0V to 0.6V DC

Input Current per Channel

(sunk by encoder device) ll mA for singleĆended drivers l8 mA for differential drivers

Maximum input Frequency

50 KHz

Encoder Data Settling Time

100 ns

Number of Outputs

8

Output Current Rating

2A sourced per output (no derating with all outputs on)

VA Rating

48W per output

384W per module

Surge Rating

4A for l0 ms

Input and Output Isolation

1500V RMS

Output Power Supply

Selectable : +5 to +24V DC

Backplane Current

800 mA at 5V DC

Output Fuses

3A rectifier fuses (Littelfuse

322003, Buss GBB003, or equivalent)

2Ć6

Summary

Chapter 2

Introducing the Absolute Encoder Module

New Position Throughput Time

200 us

New WriteĆdata Throughput Time

4.7 ms

Torque for wiring arm connections

9 inchĆpounds

Environmental Conditions

Operating Temperature

0 to 60 o

C (32 to 140 o

F)

Storage Temperature

Ć40 to 85 o

C (Ć40 to 185 o

Relative Humidity

5 to 95% (without condensation)

F)

Keying (for slot 0 only)

Between 2 and 4

Between 26 and 28

This chapter described the absolute encoder module, its functions and applications, and the processors and encoders with which it is compatible.

The next chapter tells you how to configure and install the module.

2Ć7

Chapter

3

Configuring and Installing Your Module

Chapter Objectives

Electrostatic Discharge

This chapter tells you how to: select module features by setting configuration plugs power module input circuitry and output devices key the module make wiring arm connections install the module

Electrostatic discharge can damage integrated dircuits or semiconductors in this module if you touch backplane connector pins. It can also damage the module when you set configuration plugs or switches inside the module. Avoid electrostatic discharge by observing the following precautions:

Touch a grounded object to discharge yourself before handling the module.

Do not touch the backplane connector or connector pins.

When you configure and replace internal components, do not touch other circuit components inside the module. If available, use a static-safe work station.

When not in use, keep the module in its static-shield bag.

CAUTION: Electrostatic discharge can degrade performance or damage the module. Handle as stated above.

Setting Configuration Plugs

You can choose various module features by setting configuration plugs.

The module is factory-set for use with a BCD differential output encoder.

To access the configuration plugs, lay the module on its right side and remove the cover.

The configuration plug sockets are labeled E1 through E15 on the left printed-circuit board and E1 on the right printed-circuit board. Locate the configuration plugs with the board positioned as shown in Figure 3.1

and

Figure 3.2.

Each plug is inserted on two pins of a three-pin connector.

You change the position of the plugs in a left-right or up-down direction.

3Ć1

Chapter 3

Configuring and Installing Your Module

Figure 3.1

Configuration Plug Locations and Settings (Left Board)

E13 E14

E15

E1

E2

E3

E4

E5

E6

E7

E8

E9

E10

E11

E12

Left Board

Right

13304

ConfigĆ uration

Plug

E1 through

E12

E13

E14

E15

Encoder Signal

Mode

SingleĆ ended

DifferĆ ential left right

Configuration Plug Settings

Natural

Binary

Encoder Format

Standard

Gray BCD

Gray Encoder

Rotational Direction

Increasing

Position

Decreasing

Position left left right left left left right left

3Ć2

Chapter 3

Configuring and Installing Your Module

Figure 3.2

Configuration Plug Location and Settings (Right Board)

E1

Down

Right Board

13305

Configuration Configuration Plug Settings

Plug

E1

State of Outputs After Loss of Input Power Supply

Turn

Off

Up

Last

State

Down

Selecting Encoder Format and Input Signal Mode

Set configuration plugs E1 through E12 (on the left board) to match the signal mode of each encoder input channel to the encoder. Set configuration plugs E13 and E14 (also on the left board) to match the data format of your encoder.

Selecting Encoder Rotational Direction

Use configuration plug E15 on the left board to indicate the direction of shaft rotation that causes the absolute position to increase for Gray code

3Ć3

Chapter 3

Configuring and Installing Your Module

Response to External Fault

Keying

3Ć4 encoders. This is the same as selecting “high true” or “low true” inputs from the Gray encoder.

Configuration plug E15 is factory-set in the right position. It gives an increased count when the encoder rotates clockwise when looking at the shaft. If your encoder shows a decreased count, change the plug to the left position.

If your Gray encoder has:

12 bits less than 12 bits and E15 is in this position right left right left the encoder shows: an increased count a decreased count an increased count a decreased count starting with 4,095

This configuration plug does not affect BCD or binary encoders.

Selecting State of Outputs Upon Loss of Input Power

Use configuration plug E1 on the right board to choose the state of the outputs if the module loses input power. The plug is factory-set for the outputs to turn off if input power is lost (up position). If you want the outputs to remain in their state at loss of input power, set the plug to the down position.

Except for downloading programs or commands and reporting status, the module operates independent of the host processor. In the event of a processor or I/O communications fault, the module either continues operation or its outputs turn off, depending on how you set the last state switch of the chassis in which you place the module.

If you set the last state switch to turn outputs off, the module’s outputs are turned off.

If you set the last state switch to hold outputs in last state, the module continues operating.

Plastic keying bands are shipped with each I/O chassis. These bands ensure that only a selected type of module can be placed in a particular

Power Requirements

Chapter 3

Configuring and Installing Your Module

I/O chassis module slot. They also help to align the module with the backplane connector.

Each module is slotted at its rear edge. The position of the keying bands must correspond to these slots to allow insertion of the module. Position the keying bands on the upper backplane connector between the numbers at the right of the connectors. Keying bands are only used to key slot 0 of the module. Figure 3.3 illustrates the encoder module keying positions for slot 0.

Figure 3.3

Keying Positions

0

Upper Backplane

Connectors

2-slot I/O group

1

Keying

Bands

Left

Connector

2 4

2 6

2 8

3 0

1 6

1 8

2 0

2 2

3 2

3 4

3 6

8

1 0

1 2

1 4

2

4

6

Right

Connector

2 4

2 6

2 8

3 0

1 6

1 8

2 0

2 2

3 2

3 4

3 6

8

1 0

1 2

1 4

2

4

6

12834

You must provide a minimum of two external power supplies: one to power input circuitry and one to power output devices.

Input Power Supply

Connect a +5V DC power supply for the input circuitry between terminal

21 (+) of the left wiring arm and terminal 21 (-) of the right wiring arm.

Make sure the voltage is 5V DC +.25V. The input circuitry requires a

3Ć5

Chapter 3

Configuring and Installing Your Module maximum of 300mA.

For the best system noise immunity, we recommend use of a separate, linear regulated power supply for powering the input circuitry and the encoder. You can use this supply for more than one absolute encoder module or encoder, but do not use it for otehr 5V loads such as relays.

Make sure the power supply has enough additional current capacity for the encoder.

We suggest you use extra shielded twisted pairs of wire in the encoder input cable to power the encoder. If more than one extra pair of wires remains, put them in parallel to reduce the voltage drop between the power supply and the encoder Figure 3.4.

Do not source current, such as from a power supply, into the encoder input terminals of the module. Doing so can damage input circuitry.

For the best system noise immunity, we recommend use of a separate, linear regulated power supply for powering the input circuitry and the encoder. You can use this supply for more than one absolute encoder module or encoder, but do not use it for other 5V loads such as relays.

Make sure the power supply has enough additional current capacity for the encoder.

Figure 3.4

Connecting Extra Pairs of Wires Between the Module and Encoder for Power Supply

Connections

Encoder

+5V

Supply

Common

Terminal 21 of

Left Wiring Arm

+

-

5V supply

Terminal 21 of

Right Wiring Arm

12835

3Ć6

Chapter 3

Configuring and Installing Your Module

Output Power Supply

To power the eight outputs (Figure 3.5), connect at least one +5 to +24V

DC supply to terminal 1 and terminal 6 (or 7) of the right wiring arm.

You can connect another +5 to +24V DC power supply between terminals

9 and 14 (or 15) of the right wiring arm if, for example, you need two different load supply voltages.

If you need only one supply voltage, connect a wire between terminals 1 and 9 and connect another wire between terminal 6 (or 7) and terminal 14

(or 15).

DC Output

Devices

+

+5 to 24V

DC User

Supply

-

+

+5 to 24V

DC User

Supply

-

(See Applicable

Codes and Laws)

Figure 3.5

Connection Diagram for Output Devices

+

-

+

-

Input circuitry

Right

Wiring

Arm

11

12

13

8

9

10

5

6

7

1

2

3

4

17

18

19

20

21

14

15

16

Output Supply (+5 to 24V dc)

Output 0

Output 1

Output 2

Output 3

Output Common (+5 to 24V dc)

Output Common (+5 to 24V dc)

Not Used

Output Supply (+5 to 24V dc)

Output 4

Output 5

Output 6

Output 7

Output Common (+5 to 24V dc)

Output Common (+5 to 24V dc)

Not Used

Bit 10

Bit 10 / Common

Bit 11

Bit 11 / Common

Input Common (+5V dc)

For Outputs

0 - 3

For Outputs

4 - 7

Tie Wires

Here

12838

3Ć7

Chapter 3

Configuring and Installing Your Module

WiringĆArm Connections

We recommend the following Belden cable or its equivalent to connect the encoder to the module (maximum 50 feet). Use extra twisted pairs to connect power to the encoder.

No. of No. of Twisted

Encoder Bits Pairs in Cable

8 9

10

Ć

12

11

12

15

Belden Cable No.

18 AWG 20 AWG

9775 9875

Ć

9776

9777

9876

9877

9879

Important: Tighten wiring arm connections to 9 inch-pounds of torque.

WARNING: Do not remove the wiring-arm from an operating module; it will cause the power-up bit status to change unpredictably until a valid write to the module occurs.

If swing-arm power is lost, turn on the power-up bit and disable all outputs until a valid write occurs.

Connecting a SingleĆended Output Encoder

Us e Figure 3.6

to connect a single-ended output encoder. Connect the signal line for bit 0 to terminal 1 of the left wiring arm. Connect its return to terminal 2. Connect bit 1 signal line to terminal 3 and its return to terminal 4. Continue in this way for all encoder channels.

If the encoder has less than 12 signal bits, jumper the unused input terminals. For example, if you are using a 10-bit encoder, jumper terminals 19 and 20 and terminals 17 and 18 on the right wiring arm.

3Ć8

Chapter 3

Configuring and Installing Your Module

Single-ended

Ouput Encoder

Power Supply

Common

Figure 3.6

SingleĆended Output Encoder Connection Diagram

Wiring

Arm

Bit 0

Common

Bit 1

Common

Bit 2

Common

Other bit connections not shown. Continue in this manner until you make all bit connections.

15

16

13

14

17

10

11

12

20

21

18

19

3

4

5

1

2

8

9

6

7

Wiring

Arm

15

16

17

12

13

14

20

21

18

19

9

10

11

6

7

8

3

4

5

1

2

Output

Circuitry

Bit 10

Common

Bit 11

Common

From

Encoder

If the encoder uses less than 12 bits, jumper the unused input terminals.

+ -

+5V dc Input Supply

12836

Connecting a Differential Output Encoder

Figure 3.7

is the connection diagram for a differential output encoder.

Connect the bit 0 signal line to terminal 1 and the bit 0 line to terminal 2.

Connect bit 1 to terminal 3 and the bit 1 line to terminal 4. Continue in this way for all encoder channels.

If the encoder has less than 12 signal bits, jumper the unused input terminals. For example, if you are using a 10-bit encoder, jumper terminals 19 and 20 and terminals 17 and 18 on the right wiring arm.

3Ć9

Chapter 3

Configuring and Installing Your Module

3Ć10

Differential

Ouput Encoder

Bit 0

Bit 0

Bit 1

Bit 1

Bit 2

Bit 2

Figure 3.7

Differential Output Encoder Connection Diagram

Wiring

Arm

Other bit connections not shown. Continue in this manner until you make all bit connections.

15

16

13

14

17

10

11

12

20

21

18

19

3

4

5

1

2

8

9

6

7

Wiring

Arm

15

16

17

12

13

14

20

21

18

19

9

10

11

6

7

8

3

4

5

1

2

Bit 10

Bit 10

Bit 11

Bit 11

Output

Circuitry

From

Encoder

If the encoder uses less than 12 bits, jumper the unused input terminals.

+ -

+5V dc Input Supply

12837

Connecting Output Devices

Use Figure 3.5

to connect your output devices and supply(ies). Two output commons are associated with each output group:

terminals 6 and 7 for outputs 0 through 3

terminals 14 and 15 for outputs 4 through 7

Terminals 6 and 7 are tied together internally, as are 14 and 15, so that each output group can use either terminal for that particular group.

Installing the Module

Chapter 3

Configuring and Installing Your Module

Now that you’ve determined the power requirements, keying, and wiring for your module, you can use the following procedure to install it.

Refer to the Programmable Controller Grounding and Wiring Guidelines

(pub. no. 1770-4.1) for proper grounding and wiring methods to install your module.

WARNING: Remove power from the 1771 I/O chassis backplane and wiring arm before installing or removing the module.

Failure to remove power from the backplane or wiring arm could cause module damage, degradation of performance, or injury.

Failure to remove power from the backplane could cause injury and/or equipment damage due to possible unexpected operation.

WARNING: Install the module in the I/O chassis so that both halves of the module are in the same I/O group. Failure to observe this rule will result in faulty module operation and/or damage to the module circuitry with possible injury to personnel.

CAUTION: Do not force the module into a backplane connector. If you can’t seat it with firm pressure, check the alignment and keying. You can damage the connector or the module if you force it into the connector.

1.

Remove power from the I/O chassis before inserting (or removing) the module.

2.

Open the module locking latch on the I/O chassis and insert the module into the slot keyed for it.

3.

Firmly press to seat the module into its backplane connector.

4.

Secure the module with the module locking latch.

3Ć11

Chapter 3

Configuring and Installing Your Module

Summary

This chapter told you how to select features and set configuration plugs on the absolute encoder module, and described the power requirements, keying, wiring, and installation of the module. In the next chapter you will read about block-transfer file parameters.

3Ć12

Chapter

4

Module/Processor Communication

Chapter Objectives

Block Transfer

BlockĆtransferĆwrite Data

This chapter describes file parameters for the block-transfer data files you use to write data to and read data from the absolute encoder module.

The absolute encoder module and the processor communicate through block-transfer programming. Processors that use block-transfer programming are listed below, along with the respective programming manual. Refer to the latest edition of the programming manual for a detailed description of block transfer.

Processor

MiniĆPLCĆ2

MiniĆPLCĆ2/15

MiniĆPLCĆ2/05

PLCĆ2/20

PLCĆ2/30

PLCĆ3

Programming and Operations

Manual Publication Number

1772Ć6.8.4

1772Ć6.8.2

1772Ć6.8.6

1772Ć6.8.1

1772Ć6.8.3

1772Ć6.4.1

You write data to the module in blocks. You can write 5, 10, 15 or 20 words in one block-transfer operation. Each block of five words is associated with two outputs and is identical to each other in format: words 1-5 - outputs 0 and 1 words 6-10 - outputs 2 and 3 words 11-15 - outputs 4 and 5 words 16-20 - outputs 6 and 7

The first word of each block is a control word. The last four words are preset words. The formats of the write-data words and control word 1 are shown in Figure 4.1 and are described here.

You can send a maximum of 20 words (four block of five words) in one block-transfer operation. The number of words you send to the module determines how many outputs it controls. If you want to change data for

4Ć1

Chapter 4

Module/Processor Communication outputs 4 and 5 (and the module is controlling all eight outputs), you must send 20 words to the module; you cannot send only the words associated with outputs 4 and 5.

A. WriteĆdata Words

Figure 4.1

Format of BlockĆtransferĆwrite Data

14

15

16

11

12

13

19

20

17

18

Word #1

2

3

4

5

6

7

8

9

10

17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00

OE ZT > = < > = < OE ZT > = < > = <

OE ZT >

OE ZT >

OE ZT >

=

=

=

<

<

<

>

>

>

=

=

=

<

<

<

OE ZT >

OE ZT >

OE ZT >

=

=

=

<

<

<

>

>

>

=

=

=

<

<

<

Control word for Outputs 0 and 1

Preset 0A

Preset 0B

Preset 1A

Preset 1B

Control word for Outputs 2 and 3

Preset 2A

Preset 2B

Preset 3A

Preset 3B

Control word for Outputs 4 and 5

Preset 4A

Preset 4B

Preset 5A

Preset 5B

Control word for Outputs 6 and 7

Preset 6A

Preset 6B

Preset 7A

Preset 7B

COM for

Preset 1B

COM for

Preset 1A

COM for

Preset 0B

COM for

Preset 0A

B. Format of Control

Word #1

OE ZT > = < > = < OE ZT > = < > = <

OE = Output Enable Bit

ZT = Zero Transition Bit

COM = Comparison Bits

12839

4Ć2

Chapter 4

Module/Processor Communication

Control Words

Each control word is associated with two outputs. The lower byte of control word 1 is associated with output 0. Its format is as follows:

Bits 0 through 2 are the comparison bits for output 0, preset A (greater than, less than, equal to, greater than or equal to, less than or equal to).

Bits 3 through 5 are the comparison bits for output 0, preset B.

Bit 6 is the zero transition (ZT) bit. Set this bit when an output is to be energized during a transition through 0.

Bit 7 is the output enable (OE) bit. This bit is examined along with the comparison made by the module between your presets and the absolute position of the encoder in turning on a module’s output. Although comparisons to the presets may be true, if you don’t set this bit the output is not turned on.

The upper byte of control word 1 is associated with output 1. The format of this byte is similar to the format of the lower byte:

Bits 10 through 12 are the comparison bits for output 1, preset A.

Bits 13 through 15 are the comparison bits for output 1, preset B.

Bit 16 is the ZT bit.

Bit 17 is the OE bit.

The remaining control words with their corresponding outputs are: word 6 - outputs 2 and 3 word 11 - outputs 4 and 5 word 16 - outputs 6 and 7

Preset Words

The present words define preset values for turn-on and turn-off points of the corresponding output. You program them in BCD. Each block of four preset words is associated with two outputs and is identical in format to that for outputs 0 and 1: word 2 - preset A for output 0 word 3 - preset B for output 0 word 4 - preset A for output 1 word 5 - preset B for output 1

4Ć3

Chapter 4

Module/Processor Communication

WriteĆData Throughput Time

Thewrite-data throughput time is the time between the end of a block-transfer-write operation and the module update of its outputs. The module’s response time can vary, depending on the number of outputs it controls, the type of absolute encoder you use, and if you have an offset value. The worst case is 4.7 ms. Use the following table to determine the module’s response time in milliseconds for your application.

BlockĆtransferĆread Data

Type of Encoder (with or without offset)

BCD without offset

BCD with offset

Gray code or binary without offset

Gray code or binary with offset

2 4 6 8

1.2

2.0

1.3

1.9

1.8

2.9

2.0

2.6

2.5

3.8

2.6

3.4

3.1

4.7

3.3

4.1

The processor reads data from the module and transfers it to its data table in two read-data words. The module sends only two read-data words in any one block-transfer-read operation. The format of these words is shown in Figure 4.2 and is described here:

Figure 4.2

Format of BlockĆtransferĆread Data

Word 1

Output 7

Output 6

Output 5

Output 4

Output 3

Output 2

Output 1

Output 0

17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00

Status of outputs

0

Word 2

Current Absolute Position (in BCD)

0

Code indicating which preset is in non-BCD format

Non-BCD preset flag

Unused

Write-data-valid

Loss-of-input-power

13070

The upper byte of 1 indicates the status of the eight outputs controlled by the module. The module sets each bit when the corresponding output is turned on. Refer to Appendix D for details of these bits.

The format of the lower byte of word 1 (by bit) is:

4Ć4

Programming Example

Chapter 4

Module/Processor Communication

Bit 7 is the loss-of-input-power bit. It is set when input power is lost; it is reset when power is restored and bit 6 is reset.

Bit 6 is the write-data-valid bit. It is set at power-up and when the processor changes from the program mode to the run mode; it is reset when the module receives valid data in a block-transfer-write operation.

Bit 5 is unused.

Bit 4 is the non-BCD preset flag. It is set when any preset is in non-BCD format.

Bits 3 through 0 are a binary or hexadecimal code that indicates which preset is not in BCD format. (Refer to Appendix D for the value of these bits.) The module identifies each incorrect preset in the order it finds them (one at a time). Once you correct a preset, the module continues to identify any non-BCD preset.

Word 2 indicates the current absolute position of the encoder in BCD.

Presets are interpreted by the module as absolute numbers to be compared to the absolute position of the encoder shaft; they are not interpreted as degrees of shaft rotation.

Thus, if you have a 0 to 999-position encoder, you program presets for output 3, for example, as:

Preset 3A = 200

Preset 3B = 402

There is no restriction on which mode of comparison you can use for preset A or preset B.

In this example, we assume the use of a 0 to 359-position encoder when referring to degrees of shaft rotation.

If you want to turn on output 0 between shaft positions 330 (preset A) and

005 (preset B), you set: the “greater than” and “equal to” bits for preset A the “less than” and “equal to” bits for preset B the ZT bit

4Ć5

Chapter 4

Module/Processor Communication the OE bit

Output 0 is turned on when the shaft position is greater than or equal to

330 or when the shaft position is less than or equal to 005.

If you don’t set the ZT bit in the above control word, when the encoder shaft position is 002, for example, comparison B is true, comparison A is not true, and the output is turned off. (At position 002, the shaft position is less than or equal to 005, but it is not greater than or equal to 330.) You must set the ZT bit when an output is to be energized during a transition through 0.

Another way to energize output 0 between position 330 and 005 is to give preset A a value of 006 and preset B a value of 329. Then you set: the “less than” bit for preset A the “greater than” bit for preset B the ZT bit

OE bit

In either case, you must set bit 6 (ZT) to indicate that the output should be on if either comparison A or comparison B is true.

Let’s continue this example and assume your application requirements for outputs 0 and 1 are: output 0 is to turn on at position 330 and turn off at position 005 output 1 is to turn on between position 007 and position 011

Once you define the presets for outputs 0 and 1, determine the comparison bits for each preset, and enter the data into the data file, the block of data you write to the module (five words) looks like this: binary

BCD digits

17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00

OE ZT

> = < > = < OE ZT > = < > = <

1 0

0

0

0

0

0 0 1 1

3

0

0

0

0 0 1 1

3

0

0

1

0 1 1 1

0

5

7

1

1 0

Bit #

Control

Word

Function

Control

Word

Preset 0A

Preset 0B

Preset 1A

Preset 1B

4Ć6

Chapter 4

Module/Processor Communication

Programming Considerations

When you specify the default block length (00), the following considerations apply for PLC-2 family processors:

You can and should enable the read and write instructions in the same scan (separate but equal input conditions).

The module decides which operation is performed first when both instructions are enabled in the same scan.

Alternate operation is performed in a subsequent scan.

Do not operate on transferred data until the done bit is set.

When you examine the read and write files, 64 words appear to be moved; however, the processor writes only 20 words and reads only two words in any block-transfer operation.

WARNING: When the block lengths of bidirectional block-transfer instructions are set to unequal values, do not enable the rung containing the alternate instruction until the done bit of the first transfer is set. If you enable them in the same scan, the number of words transferred may not be the number intended, invalid data could be operated upon in subsequent scans, or output devices could be controlled by invalid data. Unexpected and/or hazardous machine operation could occur. Damage to equipment and/or personal injury could result.

Summary

This chapter gave a description of the file parameters for programming block-transfer-read and -write operations for the absolute encoder module.

It also gave several programming examples and considerations for use with the absolute encoder module. The next chapter describes troubleshooting the module.

4Ć7

Offset Feature

Chapter

5

Offset Feature

Offset is a new feature of the Absolute Encoder Module (cat. no.

1771-DE, revision B). Revision A modules do not have this feature.

Offset is the difference between the 0 position of the absolute encoder and the 0 position of the machine shaft to which the encoder is connected.

You can program this value to compensate for such factors as machine wear or improper mechanical setup. You do not have to disconnect your equipment to realign the 0 position of the machine shaft with the 0 position of the absolute encoder.

Determining the Offset Value

You can find the offset value using either of two equations, depending on whether you use the 0 machine position or the 0 encoder position as your reference.

To calculate an offset value from a 0 encoder position, use this equation:

N -M = S where N = number of encoder positions, M = machine position at encoder

0, and S = offset.

To calculate an offset value from a 0 machine position, use this equation:

E - N = S where E = encoder position at machine 0, N = number of encoder positions, and S = offset.

Let’s look at an example finding the offset value with reference to 0 encoder position and 0 machine position. Assume the following:

You have a 0 to 4,095-position encoder (4,096 positions)

The machine shaft is at position 512 when the encoder is at position 0

The encoder is at position 3,584 when the machine is at position 0

5Ć1

Chapter 5

Offset Programming

Offset Words

5Ć2

In this example, the 0 machine position is “ahead” of the 0 encoder position. Depending on which equation you use (your reference point), the offset value is either positive or negative.

Offset Value From 0 Encoder Position and From 0 Machine Position

0

3584 Encoder

512

0

Machine shaft

At encoder position 0, machine shaft position is 512.

The offset is +3,584.

At machine shaft position 0, encoder position is 3,584.

The offset is Ć512.

13522

The equation (from 0 encoder position) is:

4,096 - 512 = 3,584

The offset is +3,584.

The equation (from 0 machine position) is:

3,584 - 4,096 = -512

The offset is -512.

You get the same result from programming either +3,584 or -512.

Once you determine the offset value, you need to program two write-block-transfer words. These are the last two words of the write-data block that you send to the absolute encoder module. You program them in

BCD, as you do the preset values.

Chapter 5

Offset Programming

Format of Offset Words

17 16 15 14 13 12 11 10 7 6

S

OFFSET VALUE

NO. OF ENCODER POSITIONS

5 4 3 2 1 0

The offset words are the last two words of the write-data block that you send to the absolute encoder module.

If you are controlling

2 outputs

4 outputs

6 outputs

8 outputs

The offset words are: words 6 and 7 words 11 and 12 words 16 and 17 words 21 and 22

S = sign bit. Set this bit if the offset has a negative value; reset the bit if

the offset has a positive value.

Bit #

13523

The first offset word contains the value of the offset. Bit 17 of this word is the sign bit. It indicates whether the offset is negative or positive. Set bit 17 if the offset is negative; reset it if the offset is positive.

The second offset word is the number of positions of the encoder. If you are using a 0 to 4,095-position encoder, your second offset word is 4,096.

BlockĆtransferĆwrite Data with Offset

The number of words you send to the module depends on the number of outputs the module controls. The offset feature adds two words to the total number of words you send to the module:

If the module controls:

2 outputs

4 outputs

6 outputs

8 outputs

You send:

7 words

12 words

17 words

22 words

If the module is controlling eight outputs, your block-transfer-write data now looks like this:

5Ć3

Chapter 5

Offset Programming

Figure 5.1

Format of BlockĆtransferĆwrite Data with Offset

A. Write-data words

B. Format of control

word #1

14

15

16

9

10

11

12

13

Word #1

2

3

6

7

4

5

8

17

18

19

20

21

22

17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00

OE ZT

> = < > = <

OE ZT

> = < > = <

OE ZT

OE ZT

OE ZT

S

> =

> =

> =

<

<

<

> =

> =

> =

<

<

<

OE ZT

OE ZT

OE ZT

> =

> =

> =

<

<

<

> =

> =

> =

<

<

<

COM for

Preset 1B

COM for

Preset 1A

COM for

Preset 0B

COM for

Preset 0A

OE ZT

> = < > =

OE = Output Enable Bit

ZT = Zero Transition Bit

COM = Comparison Bit

S = Offset Sign Bit

<

OE ZT

> = < > = <

Control Word for

Outputs 0 and 1

Preset 0A

Preset 0B

Preset 1A

Preset 1B

Control Word for

Outputs 2 and 3

Preset 2A

Preset 2B

Preset 3A

Preset 3B

Control Word for

Outputs 4 and 5

Preset 4A

Preset 4B

Preset 5A

Preset 5B

Control Word for

Outputs 6 and 7

Preset 6A

Preset 6B

Preset 7A

Preset 7B

Offset Value

No. of Encoder Positions

10698ĆI

BlockĆtransferĆread Data with Offset

The upper byte of word 1 indicates the status of the eight outputs controlled by the module. The module sets each bit when the corresponding output is turned on.

The lower byte of word 1 (by bit) is:

5Ć4

Chapter 5

Offset Programming

Bit 7 is the loss-of-input-power bit. It is set when input power is lost; it is reset when power is restored and bit 6 is reset.

Bit 6 is the write-data-valid bit. It is set at power-up and when the processor changes from program mode to run mode; it is reset when the module receives valid data in a block-transfer-write operation.

Bit 5 is the non-BCD offset flag. See the description of bit 0 and bit 1 below to identify the type of offset error.

Bit 4 is the non-BCD preset flag. It is set when a preset word is in non-BCD format.

Bits 3 through 0 are a binary or hexadecimal code that indicates which preset word is not in BCD format. Refer to Appendix D of the User’s

Manual for the value of these bits.

Bit 1 when set along with bit 5 identifies that the offset value is greater than the number of encoder positions.

Bit 0 identifies which offset word is in non-BCD format when bit 5 is also set.

- If bit 0 is set, the word containing the number of encoder positions is in error.

- If bit 0 is reset, the word containing the offset value is in error.

The module identifies each non-BCD word in the order it finds them

(one at a time). Once you correct the format of one word, the module continues to identify other non-BCD words.

Word 2 indicates the current position of the encoder, with the offset value, in BCD.

Figure 5.2

Format of BlockĆtransferĆread Data With Offset

Word 1

17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00

Status of Outputs

Output 7

Output 6

Output 5

Output 4

Output 3

Output 2

Output 1

Output 0

Word 2 Current Absolute Position + Offset (in BCD)

Code indicating which preset or offset word is in non-BCD format

Non-BCD preset flag

Non-BCD offset flag

Write-data-valid

Loss-of-input-power

10216ĆI

5Ć5

Chapter 5

Offset Programming

Programming Considerations with Offset

The default block lengths (00) for block-transfer instructions are 20 block-transfer-write words and two block-transfer-read words. These are the block lengths that transfer to and from the absolute encoder regardless of whether you use the offset feature.

When you have an offset value and the module is controlling eight outputs, for example, the number of words you send to the module is 22.

You must enter the numbers 22 and 2 for the block lengths of write and read data. Do not enter the default block length in your instructions if you use the module’s offset feature.

For PLC-2 family processors, do not enable the read- and write-block-transfers in the same scan when you use the offset feature.

An example program enabling the instructions in separate scans follows.

WARNING: When the block lengths of bidirectional block-transfer instructions are set to unequal values, do not enable the rung containing the alternate instruction until the done bit of the first transfer is set. If you enable them in the same scan:

the number of words transferred may not be the number intended

invalid data could be operated upon in subsequent scans

output devices could be controlled by invalid data

Unexpected and or hazardous machine operation could occur.

Damage to equipment and/or injury could result.

5Ć6

Chapter 5

Offset Programming

LADDER DIAGRAM DUMP

200

POWER-UP BIT

06

200

04

121

WRITE-DATA-VALID BIT

START

00

122

PUSHBUTTON TO CHANGE PRESETS

200

06

022

| |

06

READ

DONE

BIT

122

04

122

| |

07

FILE

DONE

BIT

044

07 15

BUFFER FILE

077

00

022

| |

07

122

| |

06

077

L

OFF00

BLOCK XFER READ

DATA ADDR:

MODULE ADDR:

BLOCK LENGTH:

FILE:

0040

220

02

0200 - 0201

077

U

OFF00

022

EN

07

122

DN

07

FILE TO FILE MOVE

COUNTER ADDR:

POSITION:

FILE LENGTH:

FILE A:

FILE R:

RATE PER SCAN

0044

001

002

0200-0201

0226-0227

002

BLOCK XFER READ

DATA ADDR:

MODULE ADDR:

BLOCK LENGTH:

FILE:

0041

220

22

0202 - 0227

FILE TO FILE MOVE

COUNTER ADDR:

POSITION:

FILE LENGTH:

FILE A:

FILE R:

0043

001

022

0202-0227

0200-0225

RATE PER SCAN 022

0044

EN

17

0044

DN

15

022

EN

06

122

DN

06

0043

EN

17

0043

DN

15

5Ć7

Chapter 5

Offset Programming

Rung 2

Rung 3

Rung 4

Rung 5

Rung 6

Rung 1 200/06 and 200/04 are returned in the read operation and latch

077/00. When 077/00 is latched, the module toggles between a read operation and a write operation.

121/00 is optional and lets the processor initiate a blockĆtransferĆwrite operation.

This rung examines the writeĆdoneĆbit (122/06) and the valid

BCD data bit (200/04) to unlatch 077/00 and begin the readĆonly operation.

This rung contains the blockĆtransferĆread instruction, conditioned by the read done bit and the write enable bit.

Use a fileĆtoĆfile move to buffer the read data. Use addresses

0226 and 0227 when making any data comparisons.

This rung contains the blockĆtransferĆwrite instruction, conditioned by the write done bit and the read enable bit.

This rung is for display purposes only.

5Ć8

Chapter

6

Troubleshooting

Chapter Objectives

Indication

ACTIVE

FAULT

ACTIVE

FAULT

ACTIVE

FAULT

ACTIVE

FAULT

In this chapter you will read how to troubleshoot your absolute encoder module using the ACTIVE (GREEN) and FAULT (red) indicators, block-transfer rungs in your ladder program, and diagnostic bits in word 2 of the read-data file.

The following table lists problems indicated by LED changes, possible causes, and recomended actions.

LED = ON LED = OFF

Description

Normal operation; module should operate when the PC goes into the RUN mode and you send presets.

Module is held reset at powerĆup; probable malfunction in adapter module or processor module.

Module has detected a hardware fault in its powerĆup diagnostic routine.

Module is not receiving DC power from the chassis backplane.

Recommended Action

None

Substitute adapter module, power supply, or processor module.

Return module for repair.

Check chassis power supply (ies).

Causes of BlockĆtransfer Errors

@

@

@

@

Observe the block-transfer rungs in your ladder diagram program. You have a block-transfer error when you observe one or both of the following:

The block-transfer error bits are intensified (PLC-3 processors).

The enable and done bits of block-transfer instructions do not intensify or they remain intensified; they should alternately turn on (intensify) and turn off.

Block-transfer errors are caused if one or more of the following are incorrect:

The module’s location (rack, group, slot) in the I/O chassis must match the rack, group, and slot of block-transfer instructions in the ladder program.

6Ć1

Chapter 6

Troubleshooting

Errors Indicated by Diagnostic

Bits

The block lengths of read- and write-block-transfer instructions should be equal (PLC-2 family processors); or if they are different lengths, do not enable the read and write instruction in the same scan.

Your conditioning instructions in block-transfer rungs allow the rungs to turn off and on.

If you’re using a PLC-2/30 processor, set the scanner for block-transfer operation.

If you’re using a PLC-3 processor, create block-transfer data files.

Examine the diagnostic bits by displaying the read block of the block-transfer-read instruction. Refer to the programming manual of your processor for the procedure.

The lower byte of the first read-data word contains the diagnostic bits.

If this bit is set:

07

06

04

Then:

The module is not receiving +5V from the input power supply; check the supply and the connections between the supply and the module.

The module has not received any blockĆtransferĆwrite data; check your blockĆtransfer instructions.

The module has examined all 16 presets (it has received write data) and has found a preset that is not in BCD; check bits 03 through 00 for the error code to determine which word contains the incorrect preset. See Appendix D for the error codes.

Summary

If you have followed the wiring and installation guidelines in chapter 3 and the block-transfer guidelines in chapter 4, you have minimized the need to troubleshoot your encoder module. If you need to troubleshoot, however, the information in this chapter can help you diagnose and correct problems.

6Ć2

BlockĆtransfer Timing

Appendix

A

BlockĆtransfer Timing for PLCĆ2

Family Processors

The time required for a block-transfer-read or -write operation for PLC-2 family processors depends on:

the system scan time(s)

the number of words to be transferred

the I/O configuration

the number of enabled block-transfer instructions in the ladder diagram

program during any program scan

A block-transfer module performs only one block-transfer operation per

I/O scan regardless of whether both read and write operations are requested. When done, the module toggles from one operation to the other in each program scan.

For a worst case calculation of the time between block transfers, assume that the number of enabled block-transfer instructions during any program scan is equal to the number of block-transfer modules in the system. Also assume that the encoder module is transferring 20 words in a write operation and two words in the alternate read operation.

The method of calculating the worst case time between block transfers is covered for the following case: PLC-2/30 remote and local systems, a

PLC-3 system, and a Mini-PLC-2/l5 controller.

PLCĆ2/30 (PLCĆ2/20) Remote System

The system scan time for a remote PLC-2/30 or PLC-2/20 system is the sum of the processor scan time, the processor I/O scan time (between processor and remote distribution panel), and the remote distribution panel I/O scan time. The remote distribution panel can process only one block-transfer operation per remote distribution panel scan.

You can calculate the worst case time between transfers under normal operating conditions in three steps.

1.

Calculate the system values that are determined by the system configuration.

AĆ1

Appendix A

Program Scan (PS) = (5 ms/1K words) x (number of program words)

Processor I/O Scan (PIO) = (0.5 ms/rack number) x (declared rack numbers)

Remote Distribution I/O Scan (RIO) = (7 ms/chassis) x (number of chassis)

Number of Words Transferred (W) = 20 words for one write operation, two words for one read operation

2.

Calculate the block-transfer time for a write operation (TW) and for a read operation (TR).

TW = (PS + PIO + 2 RIO + 0.5W + 13) ms

TR = (PS + PIO + 2 RIO + 0.5W +4) ms

These equations are valid for up to 10,000 cable feet between the remote distribution panel and remote I/O chassis for a baud rate of 57.6kBd or

5,000 cable feet at 115kBd.

3.

Calculate the worst case system time (ST) between transfers.

ST = Sum of transfer times of all block-transfer modules in a system taken worst case (read or write)

Example 1

A PLC-2/30 programmable controller is controlling 4 I/O chassis in a remote configuration with 1 assigned rack number per chassis

(Figure A.1). An encoder module is located in each chassis.

Assume the 2 words are transferred in each read operation, 20 words are transferred in each write operation, and that the ladder diagram program contains 4K words. There are no other block-transfer modules in the system.

AĆ2

Appendix A

PLC-2/30

Figure A.1

PLCĆ2/30 Remote System Example

1772-SD2

7

1

1

7

A

S

Rack 1

7

1

1

7

D

E

7

1

1

7

A

S

7

1

1

7

D

E

Rack 2

7

1

1

7

A

S

7

1

1

7

D

E

Rack 4 Rack 3

7

1

1

7

A

S

7

1

1

7

D

E

108121ĆI

We want to find the worst case time between two consecutive block-transfer-read operations from the same module in this system.

Solution:

Program length = 4K words (K = 1,024)

Number of chassis = 4 (1 assigned rack number/chassis)

AĆ3

Appendix A

Number of block-transfer words = 2 words (read) or 20 words

(write)

1.

Calculate the system values.

Processor Scan Time (PS) = (5ms/1K words) x (4K words) = 20ms

Processor I/O Scan Time (PIO)=(0.5 ms/rack number) x (4 rack numbers) = 2 ms

Remote Distribution I/O Scan Time (RIO) = (7 mx/chassis) x (4 chassis) = 28 ms

Number of Words Transferred = 2 (read) or 20 (write)

2.

Calculate the block-transfer times for a write operation and for a read operation.

TW = (PS +PIO + 2(RIO) + 0.5W + 13) ms

=(20 + 2 + 2(28) + 0.5(20) + 13) ms

=101 ms (write)

TR =(PS + PIO + 2(RIO) + 0.5W + 4) ms

=(20 + 2 + 2(28) + 0.5(2) + 4 ms

= 83 ms (read)

3.

Calculate the worst case system time (ST) between 2 consecutive block-transfer-read operations.

ST =4TW + 4TR

=4(101) + 4(83)

= 736 ms

This is the worst case time between two consecutive block-transfer-read operations in the 4-chassis remote configuration described in example 1

(one enabled encoder module in each chassis).

PLCĆ2/30 Local System

The system scan time for a local PLC-2/30 system is the program scan time plus the processor I/O scan time. Each block-transfer module is updated during a program scan.

The calculation of the worst case time between transfers can be done in three steps.

AĆ4

Appendix A

1.

Calculate the system values that are determined by the system configuration.

Program Scan (PS) = (5 ms/1K words) x (number of program words)

Processor I/O Scan (PIO) = (1 ms/rack number) x (number of declared rack numbers)

Number of words transferred (W) = 2 (read) or 20 (write)

2.

Calculate the block-transfer time (T) for the read or write operation.

T = 0.08 ms/word x number of words transferred

3.

Calculate the worst case system time (ST) between transfers.

ST =PS + PIO + T(1)(read) + T(2)(read) +T(3)(read) +...

PS + PIO + T(1)(write) + T(2)(write) + T(3)(write) +...

=2(PS + PIO) + T(1)(read) + T(2)(read) + T(3)(read) + ...

T(1)(write) + T(2)(write) + T(3)(write) + ...

Example 2

A PLC-2/30 programmable controller is controlling four I/O racks in a local configuration. Assume one block-transfer module per chassis and one assigned rack number per chassis (Figure A.2).

AĆ5

Appendix A

Figure A.2

PLCĆ2/30 Local System Example

PLC–2/30

AĆ6

1

7

7

1

A

L

Rack 1

1

7

7

1

D

E

1

7

7

1

A

L

1

7

7

1

D

E

Rack 3

1

7

7

1

A

L

1

7

7

1

D

E

Rack 2 Rack 4

1

7

7

1

A

L

1

7

7

1

D

E

10813-I

Solution:

Program length = 4K words

Number of chassis = 4 (1 assigned rack number per chassis)

Number of block-transfer words, W = 2 (read) or 20 (write)

1.

Calculate the system values.

Processor Scan Time (PS) = (5 ms/1K words) x (4K words) = 20 ms

Appendix A

Processor I/O Scan Time (PIO) = (0.5 ms/rack number) x (4 rack numbers) = 2 ms

Number of Words Transferred (W) = 2 (read) or 20 (write)

2.

Calculate the block-transfer times (T) for the read and write operation.

T

T

=0.08 ms/word x 2 words

= .16 ms (read)

=0.08 ms/word x 20 words

= 1.6 ms (write)

3.

Calculate the worst case system time (ST) between 2 consecutive block-transfer-read operations.

The module toggles to a read operation in the scan following completion of the write operation and vice versa.

ST =PS + PIO + T(1) + T(2) + T(3) + T(4)(writes)

PS + PIO + T(1) + T(2) + T(3) + T(4)(reads)

ST =2PS + 2PIO + 4T(read) + 4T(write)

=2(20) + 2(2) + 4(.16) + 4(1.6)

=40 + 4 + .64 + 6.4

=51.04 ms

This is the worst case time between two consecutive block-transfer-read operations in the 4-chassis local configuration described in example 2

(one enabled encoder module in each chassis).

MiniĆPLCĆ2/15 Controller

The Mini-PLC-2/15 scan is 15 ms for 1K program. Its I/O scan time is 5 ms. Each block-transfer module is updated during a program scan.

You can calculate the worst case time between transfers in two steps.

The facts are:

Processor scan time (PS) = 15 ms/1K words

Processor I/O scan time (PIO) = 5 ms

Number of words transferred (W) = 2 (read) or 20 (write)

1.

Calculate the block-transfer time (T) for the read and write operation.

T =0.08 ms/word x number of words transferred

AĆ7

Appendix A

The same equation is used for read and write transfer times.

2.

Calculate the worst case system time (ST) between two block-transfer-read operations.

ST =PS + PIO + T(read) + PS + PIO = T(write)

Example 3

A Mini-PLC-2/15 programmable controller is communicating with one encoder module in its I/O chassis. The ladder diagram program contains 2K words.

Solution:

The facts are:

Program length = 2K words

Processor scan time (PS) = (15 ms/1K words) x (2K words) = 30 ms

Processor I/O scan time (PIO) = 5 ms

Number of words transferred (W) = 2 (read), 20 (write)

3.

Calculate the block-transfer time (T) for the read and write operation.

T

T

=0.08 ms/word x 2 words (read)

=0.16 ms (read)

=0.08 ms/word x 20 words (write)

= 1.6 ms/(write)

4.

Calculate the worst case system item (ST) between two consecutive block-transfer-read operations.

ST =PS + PIO + T(read) + PS + PIO + T(write)

=30 + 5 + .16 + 30 + 5 + 1.6

=71.76 ms

This is the worst case time between two consecutive block-transfer-read operations for the Mini-PLC-2/15 controller.

BlockĆtransfer Timing for PLCĆ3

Family Processors

The execution time required to complete a block-transfer-read or -write operation with a PLC-3 family processor depends on the number of:

words of user program

active I/O channels on the scanner

AĆ8

Appendix A

I/O chassis entries in the rack list for the channel

I/O channels on the scanner that contain bloc-transfer modules

block-transfer modules on the channel (if the I/O chassis containing a

block-transfer module appears more than once in the I/O chassis rack list, count the module once each time the chassis appears in the rack list).)

The typical time required for the encoder module to complete a block-transfer-read/-write (bidirectional) depends on the program scan and the scanner scan as follows:

Time [read/write] = program scan + 2(scanner scan)

Program Scan: The program scan is approximately 2.5 ms per 1K words or user program when using examine on/off and block instructions.

Scanner Scan: The time required for the scanner to complete a re- or write-block transfer depends on the number of other block-transfer modules on the same scanner channel that are enabled simultaneously.

Block-transfer times typically are similar regardless of the type of block-transfer module, the number of words transferred, or whether a read or write operation is requested.

A block-transfer I/O channel is a channel that contains one or more block-transfer modules located in any chassis connected to the channel.

An I/O chassis can appear more than once in a rack list of I/O chassis.

Count the chassis and the block-transfer module(s) that it contains as often as it is listed.

The procedure for calculating block-transfer timing for a PLC-3 processor is given here followed by an example calculation:

1.

Determine the number of active I/O channels on the scanner and the number of I/O channels with block-transfer modules. Show the number of:

block-transfer modules in each I/O chassis

block-transfer I/O channels

I/O chassis entries in the rack list for each block-transfer I/O channel

active I/O channels per scanner

AĆ9

Appendix A

2.

Determine the nominal block-transfer time.

3.

Compute the approximate scanner time for each block-transfer channel.

4.

Compute the encoder re-/write-block-transfer time.

Example Computation

An example computation to determine the block-transfer timing with a

PLC-3 family processor follows. The example is based on these facts:

user program contains 20K words

channel 1 contains five I/O chassis with a total of seven block-transfer

modules including one encoder module

channel 2 contains two I/O chassis with no block-transfer modules

channel 3 contains two I/O chassis with one encoder module

channel 4 is made inactive through processor LIST

1.

Diagram the chassis connected in series to each channel (up to four) of your scanner module. Then, fill in the information called for below. Example values have been added.

1 1 1 2

Scanner

2 0 0

3

4

1

0

Make inactive through processor LIST

= I/O chassis n = number of block-transfer

modules in chassis

1

2

AĆ10

Appendix A

Description

Active I/O channels

BlockĆtransfer I/O channels

BlockĆtransfer modules on each I/O blockĆtransfer channel

I/O chassis on each blockĆtransfer

I/O channel (I/O chassis in rack list)

Number Ch1

3

2

7

5

Ch2 Ch3

0

0

1

2

Ch4

0

0

2.

Determine a time from the table. Example values have been added.

Active I/O channels containing one or more blockĆtransfer modules

Number of active I/O channels: 3

Number of active I/O channels containing one or more block-transfer modules: 2

Time, from table: 68 ms

3

4

1

2

1

40

2 3 4

52 54 58

67 68 76

98 99

123

Time (ms)

3.

Compute the scanner times for each block-transfer channel.

Example values have been added.

(CT = Channel Time).

CT=[Time] x [#BT modules] + [#I/O chassis - 1] x 9 ms

(table) on BT channel on BT channel

CT1 = [68] x [7] + [5-1] x 9

= [68] x [7] + [4] x 9

AĆ11

Appendix A

= 476 + 36

= 512 ms

CT2 = Not a block-transfer channel

CT3 = [68] x [1] + 1 x 9

= 68 + 9

= 77 ms

CT4 = Not an active channel

4.

Compute the encoder read-/write-block-transfer time. Example values have been added.

Program Scan:

Time (program)=2.5 ms/1K words x 20K words

=2.5 x 20

=50 ms

Scanner Scan:

Time (read or write) = 512 ms for channel 1 and 77 ms for channel 3

(from Step 3).

Read/Write

Time

(encoder

=Program scan + 2 [Scanner scan]

=50 + 2 [512] module in =50 + 1024 channel 1) =1074 ms

=1.1 seconds

Time =Program scan + 2 [Scanner scan]

(encoder =50 + 2[77] module in =204 ms channel 3)

AĆ12

Application Considerations

Appendix

B

Application Considerations

The absolute encoder module can control outputs within a one-count resolution (turn an output on at position 065 and off at position 066) if shaft speed does not exceed a certain limit. This speed limit depends on the number of outputs and the number of counts on the encoder. It can be found from:

S = K/N where S = maximum shaft speed for one-count resolution; K = a constant; and N = number of counts on the encoder. The value of K depends on whether you want to express shaft speed in revolutions per second (rps) or revolutions per minute (rpm).

If you control:

8 outputs

6 outputs

4 outputs

2 outputs

Then K = (for rps) OR K=(for rpm)

5000 300,000

6493

9009

14,084

389,610

540,540

845,070

For example, if you control eight outputs with a 0 to 359-count encoder, and the encoder shaft speed is given in revolutions per minute, the equation is:

300,000

S = 360 = 833 rpm

The maximum encoder shaft speed at which you can control eight outputs within a one-count resolution is 833 rpm.

Let’s consider two examples to show the importance of shaft speed, number of outputs to be controlled, and number of encoder counts in obtaining optimum module operation.

In both examples we use a 0 to 359-count encoder, all eight outputs are under control, and the output is to turn on at position 000 and off at position 001.

BĆ1

Appendix B

In the first sample (Figure B.1), we assume that the encoder shaft is turning close to the maximum allowable shaft sped according to the above equation. The shaft is in each discrete position for only 220 us, giving

360 increments (or one revolution) every 79 ms. This is equal to about

758 rpm.

In the second example (Figure B.2) , we assume a more typical shaft speed of 60 rpm, or one revolution per second. The encoder spends about 2.8

ms in each discrete position.

Figure B.1

Encoder Operating Near Maximum Speed (758 RPM)

(Shaft Position)

Encoder LSB

(Bit 0)

25

μ s

(000)

200

μ s

New

Position

Throughput

Time

A

B

C D E

(001)

Output Bit

(002)

13306

BĆ2

Appendix B

(Shaft Position)

Encoder LSB

(Bit 0)

400

μ s

(000)

2.8 ms

Figure B.2

Encoder Operating at Typical Speed (60 RPM)

(001) (002)

New

Position

Throughput

Time

Output Bit

13307

The first waveform of Figure B.1

and Figure B.2 represents the least significant bit (LSB), or bit 0, of a BCD or binary encoder. The LSB changes with every change in encoder position (one increment of shaft rotation). This bit has the highest input frequency of all encoder channels because it changes state most often. Although the LSB on standard Gray encoders does not toggle with each increment in shaft position, circuitry on the module converts the Gray code to binary code to be used by the module.

BĆ3

Appendix B

The second waveform represents the new position throughput time of the module. The third waveform represents an output programmed to turn on an actuator device (waveform high) when the encoder position is 000 and to turn it off (waveform low) when the encoder position is 001.

The new position throughput time of the module is based on the following sequence of events: a.

The encoder shaft increases one position.

b.

All 16 presets are compared to the encoder position.

c.

The module updates the outputs.

d.

The outputs are in the correct state for the given position, and the scan period is complete.

e.

The module scan begins with the next increase in the encoder shaft position and the process then repeats.

Let’s look at the first example, where the encoder is operating near maximum speed and control is maintained over a one-count resolution.

Comparing the input and output waveforms, the output bit comes on when the encoder position is almost 001 and turns off when the position is almost 002. This is due to the time needed for the software comparison.

The second example shows waveforms for a speed of one revolution per second. Control is easily maintained over a one-count resolution, and the output appears to follow the input more closely.

In both examples, the module throughput time is the same, depending only on the number of outputs to be controlled (see table below). But with increasingly lower input frequencies (slower shaft speed), the delay from change in input to output control is smaller compared to the input period of an encoder increment.

BĆ4

Appendix B

When

Controlling:

8 outputs

6 outputs

4 outputs

2 outputs

New Position

Throughput Time is:

200 us

154 us

111 us

71 us

You must take into account the fixed throughput time, the number of outputs per module, and the number of increments between the preset values when determining the appropriate machine preset values for a design shaft speed. Due to the effects shown in the first example, you may want to adjust the preset values to account for the throughput time. This is important if the module is used near its maximum design speed.

If the maximum encoder shaft speed, determined from the above equations, is too slow for your application, you should consider the following.

If you increase the input speed slightly, you can still maintain control to a one-count resolution. However, the encoder position value and the output status read by the PC may not correspond. If, for example, you request an output to turn on at position 100, for one PC scan the PC might see a position value of 099 while the output-on bit is set. The comparisons will be performed correctly, but the status of the outputs read by the PC may not correspond to the encoder position value.

This may not matter in your application if you do not use the read-data in your PC application program. However, if this is not acceptable, you may be able to trade resolution for speed. Remember that the maximum shaft speed depends on the number of encoder positions. A 0 to 4,095-count encoder has a lower maximum rpm rating than a 0 to 359-count encoder.

Similarly, a 0 to 99-count encoder turns at an even higher rotational speed to control within a one-count resolution.

You can also trade accuracy for speed. Suppose your application can tolerate having an output come on anywhere between position 030 and

035 and go off between 045 and 050. The encoder shaft may be turning fast enough to go through several positions during the module comparison processing time:

The module reads position 028 during the first module scan and leaves the output off.

BĆ5

Appendix B

During the next scan the module reads position 032 and turns the output on.

In this case you could program presets of 030 and 045 with the understanding that the change of output could occur a few increments after those positions.

Hardware RC filtering in the module input circuitry is designed to attenuate high frequency noise spikes that may pass through the optoisolators. The maximum practical input frequency to the module input terminals is limited to 50KHz.

BĆ6

Appendix

C

BlockĆtransfer Ladder Diagram Examples

Bidirectional BlockĆtransfer for

PLCĆ2 Family Processors

Figure C.1 illustrates the rungs you need to initiate a bidirectional block-transfer operation using a PLC-2 family processor.

Figure C.1

Example BlockĆtransfer Rungs for PLCĆ2 Family Processors

147

07

READ DONE BIT

BUFFER FILE

FOR DISPLAY PURPOSES ONLY

BLOCK XFER READ

DATA ADDR:

MODULE ADDR:

BLOCK LENGTH:

FILE:

0050

470

02

2400Ć2677

FILE TO FILE MOVE

COUNTER ADDR:

POSITION:

FILE LENGTH:

FILE A:

FILE R:

0061

001

002

2600Ć2601

2500Ć2501

RATE PER SCAN 002

0061

EN

17

BLOCK XFER WRITE

DATA ADDR:

MODULE ADDR:

BLOCK LENGTH:

FILE:

0051

470

00

2700Ć2777

0061

DN

15

047

EN

06

147

DN

06

FILE TO FILE MOVE

COUNTER ADDR:

POSITION:

FILE LENGTH:

FILE A:

FILE R:

0060

001

020

2600Ć2623

2700Ć2723

RATE PER SCAN 020

0060

EN

17

0060

DN

15

047

EN

07

147

DN

07

CĆ1

Appendix C

Data Address: 0050/051

This is the first possible address in the timer/counter area of the data table.

Use the first available timer/counter address for your first block-transfer module data address.

Module Address: 470

The module is located in rack 4, I/O group 7, slot 0. (Two-slot modules are addressed as being in slot 0.)

Block Length: 00

Use the default value for the maximum number of words to read (two) and write (20). Although both files appear to be 64 words long, only two words are used for read operations and 20 words are used for write operations. The remaining words are available for storage.

File: 2600/2700

This is the address of the first word of the read/write file.

Use a file-to-file move to buffer your read data. Use addresses 2500 and

2501 when making data comparisons.

Rung 4 is entered for display purposes only. You do not need this rung in your program; it allows you to look at the read- and write-data files simultaneously.

Figure C.2

shows example values entered in the read- and write-data files.

These values were chosen for a 0 to 359-count BCD encoder.

CĆ2

Appendix C

COUNTER ADDR: 060

FILE A: 2600 Ć 2623

017

018

019

020

012

013

014

009

010

011

015

016

POSITION

001

002

003

004

005

006

007

008

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

0000

READĆDATA

FILE

FILE A DATA

0200

0054

0000

0000

0000

0000

0000

0000

Figure C.2

Example ReadĆand WriteĆdata File (PLCĆ2 Family Processors)

HEXADECIMAL DATA MONITOR

FILE TO FILE MOVE

POSITION: 001

FILE LENGTH: 020

FILE R: 2700 Ć 2723

0135

0179

9E9E

0180

0224

0225

0269

9E9E

0270

0314

0315

0359

WRITEĆDATA

FILE

FILE R DATA

9E9E

0000

0044

0045

0089

9E9E

0090

0134

In these file examples, word 1 in the read-data file indicates output 1 is energized. Word 2 indicates that the current encoder position is 054.

CĆ3

Appendix C

Thus, the current encoder position is between 045 and 089 (words 4 and

5), which are the presets for output 1.

Bidirectional BlockĆtransfer for

PLCĆ3 Processors

Figure C.3 shows you how to program a bidirectional block-transfer operation using a PLC-3 processor.

Figure C.4

gives example values entered in the write-data files and displayed in the read-data files. The values were chosen for use with a single-ended, 0 to 4,095-count binary encoder.

WB010:0040

15

READ DONE BIT

WB010:0040

15

Figure C.3

Example BlockĆtransfer Rungs for PLCĆ3 Processors

BUFFER FILE

READ REQUEST

WB010:0040

17

BTR

BLOCK XFER READ

RACK :

GROUP :

MODULE :

DATA:

LENGTH =

CNTL:

002

3

0 = LOW

FB015:0001

CNTL

EN

12

CNTL

DN

0

15

CNTL

FB010:0040

ER

13

CNTL

BTW

BLOCK XFER WRITE

RACK :

GROUP :

MODULE :

DATA:

LENGTH =

CNTL:

002

3

0 = LOW

FB015:0011

EN

02

CNTL

DN

0

05

CNTL

FB010:0040

ER

03

MVF

FILES FROM A TO R

A : FB015:0001

R : FB016:0001

COUNTER :

POS/LEN =

MODE =

C0110

EN

12

C0110

DN

C0110

0/ 2

15

C0110

ALL/SCAN

ER

13

CĆ4

Appendix C

Use a file-to-file move to buffer the read data. Use B016:0001 (status) and B016:0002 (position) for all data comparisons.

Rack: 002

The module is located in rack 2.

Group: 3

The module is located in I/O group 3.

Module: 0 = low

The module is in the low slot of the I/O group. (Two-slot modules are addressed as being in slot 0.)

Data: FB015:0001/FB015:0011

This is the address of the first word of the read/write file.

Length: 0

Use the default value for the maximum number of words to read (two) and write (20).

CNTL: FB010:0040/FB010:0040

This is the address of the block-transfer control file.

CĆ5

Appendix C

RADIX = %H START = WB015:0000

WORD # 0 1

00000

00008

0000

0000

0200

0000

00016

00024

00032

00040

9E9E

2560

0000

1024

3071

0000

Figure C.4

Example ReadĆand WriteĆdata Files (PLCĆ3 Processors)

2

0693

0000

1535

9E9E

0000

3

0000

9E9E

1536

3072

0000

4

0000

0000

2047

3583

0000

5

0000

0511

9E9E

3584

0000

6

0000

0512

2048

4095

0000

7

0000

1023

2559

0000

0000

In this example:

Word 1 shows that output 1 is energized.

Word 2 indicates the current encoder position is 693.

The current position is between the presets for output 1 (words 14 and

15).

ReadĆonly BlockĆtransfer for

PLCĆ2 Family Processors

Figure C.5

shows example rungs for a read-only block-transfer operation.

Use this example to optimize your block-transfer timing.

CĆ6

Appendix C

3

Figure C.5

Example ReadĆonly BlockĆtransfer Program for PLCĆ2 Family Processors

1

LADDER DIAGRAM DUMP

200

POWER-UP BIT

06

200

WRITE-DATA-VALID BIT

121

04

00

122 200

START

PUSHBUTTON TO CHANGE PRESETS

2

06 04

BLOCK XFER READ

DATA ADDR:

MODULE ADDR:

0040

220

BLOCK LENGTH:

FILE:

00

0200 - 0277

077

U

OFF00

022

EN

07

122

DN

07

READ

DONE

BIT

122

FILE

DONE

BIT

044

BUFFER FILE

077

L

OFF00

4

07 15

FILE TO FILE MOVE

COUNTER ADDR:

POSITION:

FILE LENGTH:

FILE A:

FILE R:

0044

001

002

0200 - 0201

0226 - 0227

RATE PER SCAN 002

0044

EN

17

0044

DN

15

5

077

00

6

WRITE ENABLE BIT

BLOCK XFER WRITE

DATA ADDR:

MODULE ADDR:

BLOCK LENGTH:

FILE:

0041

220

00

0202 - 0301

022

EN

06

122

DN

06

FILE TO FILE MOVE

COUNTER ADDR:

POSITION:

FILE LENGTH:

FILE A:

FILE R:

0043

001

020

0202 - 0225

0200 - 0223

RATE PER SCAN 020

0043

EN

17

0043

DN

15

This example is a read-only operation. Use it to increase the PC's update time of the module's status.

CĆ7

Appendix C

Rung 1

Rung 2

Rung 3

Rung 4

Rung 5

Rung 6

200/06 and 200/4 are returned in the read operation and latch

077/00. When 077/00 is latched, the module toggles between a read operation and a write operation.

121/00 is optional and lets the processor initiate a blockĆtransferĆwrite operation.

This rung examines the writeĆdoneĆbit (122/06) and the valid

BCD data bit (200/04) to unlatch 077/00 and begin the readĆonly operation.

This rung contains the blockĆtransferĆread instruction.

Use a fileĆtoĆfile move to buffer the read data. Use addresses

0226 and 0227 when making any data comparisons.

A blockĆtransferĆwrite is not done unless 077/00 is on.

This rung is for display purposes only.

CĆ8

Appendix

D

Bit and Word Descriptions of Block-transfer Data

Block-transfer-write Data

Control Word for Outputs 0 and 1

Bit No.

17

16

12

11

10

15

14

13

07

06

03

02

01

05

04

00

>

=

<

>

=

<

OE

<

>

=

>

=

<

Title

OE

ZT

ZT

Description

Output enable bit - set this bit if you want output 1 turned on when comparisons with presets 1A and 1B are true.

Zero transition bit - set this bit when you want output 1 energized during a transition through position 000.

Comparison bit for preset 1B

Comparison bit for preset 1B

Comparison bit for preset 1B

Comparison bit for preset 1A

Comparison bit for preset 1A

Comparison bit for preset 1A

Output enable bit - set this bit if you want output 0 turned on when comparisons with preset 1A and 1B are true.

Zero transition bit - set this bit when you want output 0 energized during a transition through position 000.

Comparison bit for preset 0B

Comparison bit for preset 0B

Comparison bit for preset 0B

Comparison bit for preset 0A

Comparison bit for preset 0A

Comparison bit for preset 0A

DĆ1

Appendix D

Block-transfer-read Data

Preset Words

Word

No.

Description

2 Preset value A for output 0

3 Preset value B for output 0

4 Preset value A for output 1

5 Preset value B for output 1

7 Preset value A for output 2

8 Preset value B for output 2

9 Preset value A for output 3

10 Preset value B for output 3

12 Preset value A for output 4

13 Preset value B for output 4

14 Preset value A for output 5

15 Preset value B for output 5

17 Preset value A for output 6

18 Preset value B for output 6

19 Preset value A for output 7

20 Preset value B for output 7

Read-data Words

Word No.

1

Bit No.

17

16

13

12

11

15

14

10

07

Status of output 7

Status of output 6

Description

Status of output 5

Status of output 4

Status of output 3

Status of output 2

Status of output 1

Status of output 0

Loss-of-input-power bit - bit is set when input power is lost; it is reset when power is restored and bit 6 is reset.

DĆ2

Appendix D

14

15

12

13

17

18

7

8

9

10

Word No.

2

Bit No.

Description

06 Write-data-valid bit - bit is set at power up and when the processor changes from program to run mode; it is reset when the module receives valid write data.

Unused 05

04 Non-BCD preset flag - bit is set when any preset is in non-BCD format.

03 through 00 These bits are binary or hexadecimal code that indicates which of the 16 presets is not in

BCD format. Refer to the next section for details of these bits.

17 through 00 Current absolute position of encoder in BCD

Value of Diagnostic Bits 00 through 03

If non-BCD digit is in word:

2

3

4

5

Then it is preset:

0A

0B

1A

1B

And the Hex error code is:

0

1

2

3

And the binary equivalent is:

0000

0001

0010

0011

5A

5B

4A

4B

6A

6B

2A

2B

3A

3B

A

B

8

9

C

D

4

5

6

7

1000

1001

1010

1011

1100

1101

0100

0101

0110

0111

DĆ3

Appendix D

If non-BCD digit is in word:

19

20

Then it is preset:

7A

7B

And the Hex error code is:

E

F

And the binary equivalent is:

1110

1111

DĆ4

Appendix

E

Connection Diagrams for AllenĆBradley Encoders

Connection Diagrams for

AllenĆBradley Encoders

0 to 359Ćcount, 10Ćbit, BCD,

SingleĆended Output

Figures E.1 throug h Figure E.3

show you how to connect several

Allen-Bradley encoders to the absolute encoder module:

Figure E.1

shows you how to connect a Bulletin 845A encoder, 0 to

359-count, 10-bit, BCD, single-ended output encoder.

Figure E.2

shows you how to connect a Bulletin 845A encoder, 0 to

255-count, 8-bit, Standard Gray, single-ended output encoder.

Figure E.3 sh ows you the connections for a Bulletin 845C encoder, 0 to

359-count, 10-bit, BCD, single-ended output, latching encoder.

Follow these guidelines:

Make the wht/orn wire (pin V) an open connection.

The encoder counts up in a counterclockwise direction if you make the wht/yel wire (pinQ) an open connection or if you connect it to +5V; if you connect it to ground, the encoder counts up in a clockwise direction.

Signal common wht/blk (pin W) and ground blk (pin X) are internally connected on the encoder.

Jumper the unused most-significant-bit input terminals.

EĆ1

Appendix E

Figure E.1

Connection Diagram for AllenĆBradley Encoder, Bulletin 845A (BCD)

1771ĆDE

Left

Wiring

Arm

(Pin R) BRN DECADE 1 - 1

(Pin K) ORN DECADE 1 - 2

(Pin E) YEL DECADE 1 - 4

(Pin A) GRN DECADE 1 - 8

(Pin B) BLU DECADE 2-1

(Pin G) VIO DECADE 2 - 2

(Pin C) GRAY DECADE 2 - 4

(Pin H) WHT DECADE 2 - 8

(Pin D) WHT / RED DECADE 3 - 1

(Pin J) WHT/BRN DECADE 3 - 2

(Pin Z) RED +5V dc

13

14

15

16

10

11

8

9

12

5

6

7

1

2

3

4

17

18

19

20

21

11

12

13

8

9

10

5

6

7

1

2

3

4

17

18

19

14

15

16

20

21

Right

Wiring

Arm

(Pin X) BLK GND

(Pin W) WHT / BLK SIGNAL COM

+

-

+5V dc Input Supply

Pin locations ( ) are shown for encoders without colored wires.

13308

EĆ2

Appendix E

0 to 255Ćcount, 8Ćbit, Standard

Gray, SingleĆended Output

Follow these guidelines:

Set configuration plug E15 on the absolute encoder module to the right position for increasing position.

Signal common (pin X) and ground (pin W) are internally connected on the encoder.

The encoder counts up in a clockwise direction when you connect pin J instead of pin H.

Leave pins V and Q unconnected.

Jumper the unused most-significant-bit input terminals.

Figure E.2

Connection Diagram for AllenĆBradley Encoder, Bulletin 845A (Standard Gray)

1771ĆDE

Left

Arm

Pin A G0

Pin B G1

Pin C G2

Pin D G3

Pin E G4

Pin F G5

Pin G G6

Pin H G7

Pin Z +5V dc

16

17

18

19

20

21

10

11

12

13

14

15

6

7

4

5

8

9

1

2

3

16

17

18

19

20

21

10

11

12

13

14

15

7

8

9

5

6

3

4

1

2

Right

Arm

Pin X

Pin W

Sig Com

Ground

+

-

+5V dc Input Supply

13309

EĆ3

Appendix E

0 to 359Ćcount, 10Ćbit, BCD,

SingleĆended Output, Latching

Follow these guidelines:

The encoder counts up in a counterclockwise direction if you make pin

H an open connection or if you connect it to +5V; if you connect it to ground, the encoder counts up in a clockwise direction.

Pins P, N, and V are internally connected on the encoder.

Pins U, Z, T, and M are internally connected on the encode.

Encoder output requires +5V DC; jumper pins P, N, and V to pin Y.

Leave pin L unconnected.

Ground pin X for normal operation.

Leave pins J, D, and Q unconnected.

Jumper the unused most-significant-bit input terminals.

EĆ4

Appendix E

Figure E.3

Connection Diagram for AllenĆBradley Encoder, Bulletin 845C (BCD)

1771ĆDE

Left

Wiring

Arm

Pin S D1 - 1

Pin W D1 - 2

Pin R D1 - 4

Pin K D1 - 8

Pin E D2 - 1

Pin A D2 - 2

Pin F D2 - 4

Pin B D2 - 8

Pin G D3 - 1

Pin C D3 - 2

Pins P, N, V +5V dc

16

17

18

13

14

15

19

20

21

10

11

12

7

8

9

4

5

6

1

2

3

16

17

18

13

14

15

19

20

21

10

11

12

7

8

9

4

5

6

1

2

3

Right

Wiring

Arm

Pins U, Z,T,M signal common

Pin X

+

-

+5V dc Input Supply

13310

EĆ5

Appendix

F

Glossary

This glossary defines terms pertaining to Allen–Bradley Absolute

Encoder Modules. For abroader glossary of programmable controller words, refer to our Programmable Controller Terms (publication no.

PCGI–7.2).

ABSOLUTE ENCODER:

An encoder with a unique digital output code for each increment of shaft rotation

BIDIRECTIONAL BLOCK TRANSFER:

The performance of alternating read and write operations between an intelligent I/O module and the processor data table

DIFFERENTIAL OUTPUT ENCODER:

An encoder using differential line driver output devices that have a bit x and bit x output signals

ENCODER DATA SETTLING TIME:

The time required for encoder data to settle to reflect a new position

GRAY CODE:

A binary numbering system modified so that only 1 bit changes as the counting number increases.

MAXIMUM ENCODER SHAFT SPEED:

The maximum speed at which the encoder shaft can turn to give a one–count resolution while controlling a particular number of outputs.

NEW POSITION THROUGHPUT TIME:

The time between a certain state being applied to the input terminals and

FĆ1

Appendix F the appropriate response occurring at the output terminals; it depends on the number of outputs the module is controlling

NEW WRITE–DATA THROUGHPUT TIME:

The time between the end of a block–transfer–write operation and the module update of outputs

ONE–COUNT RESOLUTION:

The ability of the module to perform within one increment of shaft rotation; for example, turn on an output at position 007 and off at position

008

PRESET VALUE:

The value against which the absolute position of the encoder is compared to control an output

SINGLE–ENDED OUTPUT ENCODER:

An encoder using single–ended (totem pole or open collector) output devices that have bit x and common output signals. Each bit may have a common terminal, or all common terminals may be tied to the power supply ground or common terminal in the encoder.

FĆ2

Index

Symbols

**Empty**, 2Ć1 , 2Ć2 , 3Ć9 , DĆ1

A

Application Considerations, BĆ1

B

Block-tranfer-write Data, 4Ć1

Block-transfer Timing

PLC-2/15, AĆ7

PLC-2/30 Local System, AĆ4

PLC-2/30 Remote System, AĆ1

PLC-3, AĆ9

Block-transfer-read Data, DĆ2

Block-transfer-read-Data, 4Ć4

C

Cabling, 3Ć8

Compatible Encoders, 2Ć2

Configuration Plugs, Location

Setting, 3Ć3

Settings, 3Ć2

Connections

Output Devices, 3Ć10

Power Supplies, 3Ć5

Control Words, 4Ć3 , DĆ1

D

Diagnostic Bits, DĆ3

E

Encoder, 3Ć9

Format, 2Ć2 , 3Ć3

Input Signal Mode, 3Ć3

Example Applications, 2Ć1

F

Fuses, 2Ć3 , 2Ć6

G

Glossary, FĆ1

I

Installation, 3Ć11

K

Keying, 2Ć7 , 3Ć4

M

Module Functions, 2Ć1 module throughput time, BĆ4

O

one-count resolution, BĆ1

P

Power Requirements

Input, 2Ć6

Output, 3Ć5

Output, 2Ć6 , 3Ć7

Preset Words, 4Ć3 , DĆ2

Programming Considerations, 4Ć7

Programming Example, 4Ć5

S

Specifications, 2Ć6

State of Output Upon Less of Input Power,

2Ć2

Status Indicator, 2Ć3

T

Terminal Identification, 2Ć5

Troubleshooting, 6Ć1

AllenĆBradley, a Rockwell Automation Business, has been helping its customers improve productivity and quality for more than 90 years. We design, manufacture and support a broad range of automation products worldwide. They include logic processors, power and motion control devices, operator interfaces, sensors and a variety of software. Rockwell is one of the world's leading technology companies.

Worldwide representation.

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AllenĆBradley Headquarters, 1201 South Second Street, Milwaukee, WI 53204 USA, Tel: (1) 414 382Ć2000 Fax: (1) 414 382Ć4444

Publication 1771-6.5.32 January 1986

PN 955096-76

Copyright 1986 AllenĆBradley Company, Inc. Printed in USA

Publication 1771-6.5.32 January 1986