Texas Instruments | LM628/LM629 Precision Motion Controller (Rev. C) | Datasheet | Texas Instruments LM628/LM629 Precision Motion Controller (Rev. C) Datasheet

Texas Instruments LM628/LM629 Precision Motion Controller (Rev. C) Datasheet
LM628, LM629
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LM628/LM629 Precision Motion Controller
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FEATURES
DESCRIPTION
•
The LM628/LM629 are dedicated motion-control
processors designed for use with a variety of DC and
brushless
DC
servo
motors,
and
other
servomechanisms which provide a quadrature
incremental position feedback signal. The parts
perform the intensive, real-time computational tasks
required for high performance digital motion control.
The host control software interface is facilitated by a
high-level command set. The LM628 has an 8-bit
output which can drive either an 8-bit or a 12-bit
DAC. The components required to build a servo
system are reduced to the DC motor/actuator, an
incremental encoder, a DAC, a power amplifier, and
the LM628. An LM629-based system is similar,
except that it provides an 8-bit PWM output for
directly driving H-switches. The parts are fabricated in
NMOS and packaged in a 28-pin dual in-line package
or a SOIC-24 package (LM629 only). Both 6 MHz and
8 MHz maximum frequency versions are available
with the suffixes -6 and -8, respectively, used to
designate the versions. They incorporate an SDA
core processor and cells designed by SDA.
1
2
•
•
•
•
•
•
•
•
•
•
•
32-bit Position, Velocity, And Acceleration
Registers
Programmable Digital PID Filter with 16-bit
Coefficients
Programmable Derivative Sampling Interval
8- or 12-bit DAC Output Data (LM628)
8-bit Sign-magnitude PWM Output Data
(LM629)
Internal Trapezoidal Velocity Profile Generator
Velocity, Target Position, and Filter
Parameters may be Changed During Motion
Position and Velocity Modes of Operation
Real-time Programmable Host Interrupts
8-bit Parallel Asynchronous Host Interface
Quadrature Incremental Encoder Interface with
Index Pulse Input
Available in a 28-pin Dual In-line Package or a
SOIC-24 Package (LM629 Only)
Figure 1. Block Diagram
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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Connection Diagrams
LM628N
LM629N
LM629M
*Do not connect.
Figure 2. See Package Number DW or N
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings (1) (2)
Voltage at Any Pin with
−0.3V to +7.0V
Respect to GND
−65°C to +150°C
Ambient Storage Temperature
Lead Temperature
28-pin PDIP Package (Soldering, 4 sec.)
24-pin SOIC Package (Soldering, 10 sec.)
Maximum Power Dissipation (TA ≤ 85°C) (3)
ESD Tolerance
(1)
(2)
(3)
260°C
300°C
605 mW
(CZAP = 120 pF, RZAP = 1.5k)
1000V
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not
apply when operating the device beyond the above Operating Ratings.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
When operating at ambient temperatures above 70°C, the device must be protected against excessive junction temperatures. Mounting
the package on a printed circuit board having an area greater than three square inches and surrounding the leads and body with wide
copper traces and large, uninterrupted areas of copper, such as a ground plane, suffices. The 28-pin DIP (N) and the 24-pin surface
mount package (M) are molded plastic packages with solid copper lead frames. Most of the heat generated at the die flows from the die,
through the copper lead frame, and into copper traces on the printed circuit board. The copper traces act as a heat sink. Double-sided
or multi-layer boards provide heat transfer characteristics superior to those of single-sided boards.
Operating Ratings
−40°C < TA < +85°C
Temperature Range
Clock Frequency
LM628N-6, LM629N-6, LM629M-6
1.0 MHz < fCLK < 6.0 MHz
LM628N-8, LM629N-8, LM629M-8
1.0 MHz < fCLK < 8.0 MHz
VDD Range
2
4.5V < VDD < 5.5V
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DC Electrical Characteristics
(VDD and TA per Operating Ratings; fCLK = 6 MHz)
Symbol
IDD
Parameter
Tested Limits
Conditions
Supply Current
Min
Outputs Open
Max
110
Units
mA
INPUT VOLTAGES
VIH
Logic 1 Input Voltage
VIL
Logic 0 Input Voltage
IIN
Input Currents
2.0
0 ≤ VIN ≤ VDD
−10
2.4
V
0.8
V
10
μA
OUTPUT VOLTAGES
VOH
Logic 1
IOH = −1.6 mA
VOL
Logic 0
IOL = 1.6 mA
IOUT
TRI-STATE Output Leakage Current
0 ≤ VOUT ≤ VDD
−10
V
0.4
V
10
μA
AC Electrical Characteristics
(VDD and TA per Operating Ratings; fCLK = 6 MHz; CLOAD = 50 pF; Input Test Signal tr = tf = 10 ns)
Timing Interval
T#
Tested Limits
Min
Max
Units
ENCODER AND INDEX TIMING (See Figure 3)
Motor-Phase Pulse Width
T1
μs
T2
μs
Dwell-Time per State
Index Pulse Setup and Hold
(Relative to A and B Low)
T3
0
μs
LM628N-6, LM629N-6,
LM629M-6
T4
78
ns
LM628N-8, LM629N-8,
LM629M-8
T4
57
ns
LM628N-6, LM629N-6,
LM629M-6
T5
166
ns
LM628N-8, LM629N-8,
LM629M-8
T5
125
ns
CLOCK AND RESET TIMING (See Figure 4)
Clock Pulse Width
Clock Period
T6
μs
Reset Pulse Width
STATUS BYTE READ TIMING (See Figure 5)
Chip-Select Setup/Hold Time
T7
0
ns
Port-Select Setup Time
T8
30
ns
Port-Select Hold Time
T9
30
Read Data Access Time
T10
Read Data Hold Time
T11
RD High to Hi-Z Time
T12
ns
180
0
ns
ns
180
ns
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AC Electrical Characteristics (continued)
(VDD and TA per Operating Ratings; fCLK = 6 MHz; CLOAD = 50 pF; Input Test Signal tr = tf = 10 ns)
Timing Interval
T#
Tested Limits
Min
Max
Units
COMMAND BYTE WRITE TIMING (See Figure 6)
Chip-Select Setup/Hold Time
T7
0
ns
Port-Select Setup Time
T8
30
ns
Port-Select Hold Time
T9
30
Busy Bit Delay
T13
WR Pulse Width
T14
Write Data Setup Time
Write Data Hold Time
ns
See (1)
ns
100
ns
T15
50
ns
T16
120
ns
DATA WORD READ TIMING (See Figure 7)
Chip-Select Setup/Hold Time
T7
0
ns
Port-Select Setup Time
T8
30
ns
Port-Select Hold Time
T9
30
Read Data Access Time
T10
Read Data Hold Time
T11
RD High to Hi-Z Time
T12
180
ns
Busy Bit Delay
T13
See (1)
ns
Read Recovery Time
T17
120
ns
Chip-Select Setup/Hold Time
T7
0
ns
Port-Select Setup Time
T8
30
ns
Port-Select Hold Time
T9
30
Busy Bit Delay
T13
WR Pulse Width
T14
Write Data Setup Time
Write Data Hold Time
Write Recovery Time
ns
180
0
ns
ns
DATA WORD WRITE TIMING (See Figure 8)
(1)
ns
See (1)
ns
100
ns
T15
50
ns
T16
120
ns
T18
120
ns
In order to read the busy bit, the status byte must first be read. The time required to read the busy bit far exceeds the time the chip
requires to set the busy bit. It is, therefore, impossible to test actual busy bit delay. The busy bit is ensured to be valid as soon as the
user is able to read it.
Figure 3. Quadrature Encoder Input Timing
4
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Figure 4. Clock and Reset Timing
Figure 5. Status Byte Read Timing
Figure 6. Command Byte Write Timing
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Figure 7. Data Word Read Timing
Figure 8. Data Word Write Timing
6
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Pinout Description
(See Connection Diagrams) Pin numbers for the 24-pin surface mount package are indicated in parentheses.
Pin 1 (17), Index (IN) Input: Receives optional index pulse from the encoder. Must be tied high if not used. The
index position is read when Pins 1, 2, and 3 are low.
Pins 2 and 3 (18 and 19), Encoder Signal (A, B) Inputs: Receive the two-phase quadrature signals provided
by the incremental encoder. When the motor is rotating in the positive (“forward”) direction, the signal at Pin 2
leads the signal at Pin 3 by 90 degrees. Note that the signals at Pins 2 and 3 must remain at each encoder state
(See Figure 10) for a minimum of 8 clock periods in order to be recognized. Because of a four-to-one resolution
advantage gained by the method of decoding the quadrature encoder signals, this corresponds to a maximum
encoder-state capture rate of 1.0 MHz (fCLK = 8.0 MHz) or 750 kHz (fCLK = 6.0 MHz). For other clock frequencies
the encoder signals must also remain at each state a minimum of 8 clock periods.
Pins 4 to 11 (20 to 24 and 2 to 4), Host I/O Port (D0 to D7): Bi-directional data port which connects to host
computer/processor. Used for writing commands and data to the LM628, and for reading the status byte and data
from the LM628, as controlled by CS (Pin 12), PS (Pin 16), RD (Pin 13), and WR (Pin 15).
Pin 12 (5), Chip Select (CS ) Input: Used to select the LM628 for writing and reading operations.
Pin 13 (6), Read (RD ) Input: Used to read status and data.
Pin 14 (7), Ground (GND): Power-supply return pin.
Pin 15 (8), Write (WR ) Input: Used to write commands and data.
Pin 16 (9), Port Select (PS ) Input: Used to select command or data port. Selects command port when low,
data port when high. The following modes are controlled by Pin 16:
1. Commands are written to the command port (Pin 16 low),
2. Status byte is read from command port (Pin 16 low), and
3. Data is written and read via the data port (Pin 16 high).
Pin 17 (10), Host Interrupt (HI) Output: This active-high signal alerts the host (via a host interrupt service
routine) that an interrupt condition has occurred.
Pins 18 to 25, DAC Port (DAC0 to DAC7): Output port which is used in three different modes:
1. LM628 (8-bit output mode): Outputs latched data to the DAC. The MSB is Pin 18 and the LSB is Pin 25.
2. LM628 (12-bit output mode): Outputs two, multiplexed 6-bit words. The less-significant word is output first.
The MSB is on Pin 18 and the LSB is on Pin 23. Pin 24 is used to demultiplex the words; Pin 24 is low for
the less-significant word. The positive-going edge of the signal on Pin 25 is used to strobe the output data.
Figure 9 shows the timing of the multiplexed signals.
3. LM629 (sign/magnitude outputs): Outputs a PWM sign signal on Pin 18 (11 for surface mount), and a PWM
magnitude signal on Pin 19 (13 for surface mount). Pins 20 to 25 are not used in the LM629. Figure 12
shows the PWM output signal format.
Pin 26 (14), Clock (CLK) Input: Receives system clock.
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Pin 27 (15), Reset (RST) Input: Active-low, positive-edge triggered, resets the LM628 to the internal conditions
shown below. Note that the reset pulse must be logic low for a minimum of 8 clock periods. Reset does the
following:
1. Filter coefficient and trajectory parameters are zeroed.
2. Sets position error threshold to maximum value (7FFF hex), and effectively executes command LPEI.
3. The SBPA/SBPR interrupt is masked (disabled).
4. The five other interrupts are unmasked (enabled).
5. Initializes current position to zero, or “home” position.
6. Sets derivative sampling interval to 2048/fCLK or 256 μs for an 8.0 MHz clock.
7. DAC port outputs 800 hex to “zero” a 12-bit DAC and then reverts to 80 hex to “zero” an 8-bit DAC.
Immediately after releasing the reset pin from the LM628, the status port should read “00”. If the reset is
successfully completed, the status word will change to hex “84” or “C4” within 1.5 ms. If the status word has not
changed from hex “00” to “84” or “C4” within 1.5 ms, perform another reset and repeat the above steps. To be
certain that the reset was properly performed, execute a RSTI command. If the chip has reset properly, the
status byte will change from hex “84” or “C4” to hex “80” or “C0”. If this does not occur, perform another reset
and repeat the above steps.
Pin 28 (16), Supply Voltage (VDD): Power supply voltage (+5V).
Figure 9. 12-Bit Multiplexed Output Timing
8
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THEORY OF OPERATION
INTRODUCTION
The typical system block diagram (See Figure 1) illustrates a servo system built using the LM628. The host
processor communicates with the LM628 through an I/O port to facilitate programming a trapezoidal velocity
profile and a digital compensation filter. The DAC output interfaces to an external digital-to-analog converter to
produce the signal that is power amplified and applied to the motor. An incremental encoder provides feedback
for closing the position servo loop. The trapezoidal velocity profile generator calculates the required trajectory for
either position or velocity mode of operation. In operation, the LM628 subtracts the actual position (feedback
position) from the desired position (profile generator position), and the resulting position error is processed by the
digital filter to drive the motor to the desired position. Table 1 provides a brief summary of specifications offered
by the LM628/LM629:
POSITION FEEDBACK INTERFACE
The LM628 interfaces to a motor via an incremental encoder. Three inputs are provided: two quadrature signal
inputs, and an index pulse input. The quadrature signals are used to keep track of the absolute position of the
motor. Each time a logic transition occurs at one of the quadrature inputs, the LM628 internal position register is
incremented or decremented accordingly. This provides four times the resolution over the number of lines
provided by the encoder. See Figure 10. Each of the encoder signal inputs is synchronized with the LM628 clock.
The optional index pulse output provided by some encoders assumes the logic-low state once per revolution. If
the LM628 is so programmed by the user, it will record the absolute motor position in a dedicated register (the
index register) at the time when all three encoder inputs are logic low.
If the encoder does not provide an index output, the LM628 index input can also be used to record the home
position of the motor. In this case, typically, the motor will close a switch which is arranged to cause a logic-low
level at the index input, and the LM628 will record motor position in the index register and alert (interrupt) the
host processor. Permanently grounding the index input will cause the LM628 to malfunction.
Table 1. System Specifications Summary
Position Range
−1,073,741,824 to 1,073,741,823 counts
Velocity Range
0 to 1,073,741,823/216 counts/sample; ie, 0 to 16,383 counts/sample, with a resolution of 1/216 counts/sample
Acceleration Range
0 to 1,073,741,823/216 counts/sample/sample; ie, 0 to 16,383 counts/sample/sample, with a resolution of 1/216
counts/sample/sample
Motor Drive Output
LM628: 8-bit parallel output to DAC, or 12-bit multiplexed output to DAC
LM629: 8-bit PWM sign/magnitude signals
Operating Modes
Position and Velocity
Feedback Device
Incremental Encoder (quadrature signals; support for index pulse)
Control Algorithm
Proportional Integral Derivative (PID) (plus programmable integration limit)
Sample Intervals
Derivative Term: Programmable from 2048/fCLK to (2048 * 256)/fCLK in steps of 2048/fCLK (256 to 65,536 μs for
an 8.0 MHz clock).
Proportional and Integral: 2048/fCLK
Figure 10. Quadrature Encoder Signals
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Figure 11. Typical Velocity Profiles
VELOCITY PROFILE (TRAJECTORY) GENERATION
The trapezoidal velocity profile generator computes the desired position of the motor versus time. In the position
mode of operation, the host processor specifies acceleration, maximum velocity, and final position. The LM628
uses this information to affect the move by accelerating as specified until the maximum velocity is reached or
until deceleration must begin to stop at the specified final position. The deceleration rate is equal to the
acceleration rate. At any time during the move the maximum velocity and/or the target position may be changed,
and the motor will accelerate or decelerate accordingly. Figure 11 illustrates two typical trapezoidal velocity
profiles. Figure 11(a) shows a simple trapezoid, while Figure 11(b) is an example of what the trajectory looks like
when velocity and position are changed at different times during the move.
When operating in the velocity mode, the motor accelerates to the specified velocity at the specified acceleration
rate and maintains the specified velocity until commanded to stop. The velocity is maintained by advancing the
desired position at a constant rate. If there are disturbances to the motion during velocity mode operation, the
long-time average velocity remains constant. If the motor is unable to maintain the specified velocity (which could
be caused by a locked rotor, for example), the desired position will continue to be increased, resulting in a very
large position error. If this condition goes undetected, and the impeding force on the motor is subsequently
released, the motor could reach a very high velocity in order to catch up to the desired position (which is still
advancing as specified). This condition is easily detected; see commands LPEI and LPES.
All trajectory parameters are 32-bit values. Position is a signed quantity. Acceleration and velocity are specified
as 16-bit, positive-only integers having 16-bit fractions. The integer portion of velocity specifies how many counts
per sampling interval the motor will traverse. The fractional portion designates an additional fractional count per
sampling interval. Although the position resolution of the LM628 is limited to integer counts, the fractional counts
provide increased average velocity resolution. Acceleration is treated in the same manner. Each sampling
interval the commanded acceleration value is added to the current desired velocity to generate a new desired
velocity (unless the command velocity has been reached).
One determines the trajectory parameters for a desired move as follows. If, for example, one has a 500-line shaft
encoder, desires that the motor accelerate at one revolution per second per second until it is moving at 600 rpm,
and then decelerate to a stop at a position exactly 100 revolutions from the start, one would calculate the
trajectory parameters as follows:
let
P = target position (units = encoder counts)
let
R = encoder lines * 4 (system resolution)
then R = 500 * 4 = 2000
10
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P = 2000 * desired number of revolutions
P = 2000 * 100 revs = 200,000 counts (value to load)
P (coding) = 00030D40 (hex code written to LM628)
let
V = velocity (units = counts/sample)
let
T = sample time (seconds) = 341 μs (with 6 MHz clock)
let
C = conversion factor = 1 minute/60 seconds
then V = R * T * C * desired rpm
and
V = 2000 * 341E−6 * 1/60 * 600 rpm
V = 6.82 counts/sample
V (scaled) = 6.82 * 65,536 = 446,955.52
V (rounded) = 446,956 (value to load)
V (coding) = 0006D1EC (hex code written to LM628)
let
A = acceleration (units = counts/sample/sample)
A = R * T * T * desired acceleration (rev/sec/sec)
then A = 2000 * 341E−6 * 341E-6 * 1 rev/sec/sec
and
A = 2.33E−4 counts/sample/sample
A (scaled) = 2.33E−4 * 65,536 = 15.24
A (rounded) = 15 (value to load)
A (coding) = 0000000F (hex code written to LM628)
The above position, velocity, and acceleration values must be converted to binary codes to be loaded into the
LM628. The values shown for velocity and acceleration must be multiplied by 65,536 (as shown) to adjust for the
required integer/fraction format of the input data. Note that after scaling the velocity and acceleration values,
literal fractional data cannot be loaded; the data must be rounded and converted to binary. The factor of four
increase in system resolution is due to the method used to decode the quadrature encoder signals, see
Figure 10.
PID COMPENSATION FILTER
The LM628 uses a digital Proportional Integral Derivative (PID) filter to compensate the control loop. The motor is
held at the desired position by applying a restoring force to the motor that is proportional to the position error,
plus the integral of the error, plus the derivative of the error. The following discrete-time equation illustrates the
control performed by the LM628:
where
•
u(n) is the motor control signal output at sample time n, e(n) is the position error at sample time n, n′ indicates
sampling at the derivative sampling rate, and kp, ki, and kd are the discrete-time filter parameters loaded by
the users.
(1)
The first term, the proportional term, provides a restoring force porportional to the position error, just as does a
spring obeying Hooke's law. The second term, the integration term, provides a restoring force that grows with
time, and thus ensures that the static position error is zero. If there is a constant torque loading, the motor will
still be able to achieve zero position error.
The third term, the derivative term, provides a force proportional to the rate of change of position error. It acts
just like viscous damping in a damped spring and mass system (like a shock absorber in an automobile). The
sampling interval associated with the derivative term is user-selectable; this capability enables the LM628 to
control a wider range of inertial loads (system mechanical time constants) by providing a better approximation of
the continuous derivative. In general, longer sampling intervals are useful for low-velocity operations.
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In operation, the filter algorithm receives a 16-bit error signal from the loop summing-junction. The error signal is
saturated at 16 bits to ensure predictable behavior. In addition to being multiplied by filter coefficient kp, the error
signal is added to an accumulation of previous errors (to form the integral signal) and, at a rate determined by
the chosen derivative sampling interval, the previous error is subtracted from it (to form the derivative signal). All
filter multiplications are 16-bit operations; only the bottom 16 bits of the product are used.
The integral signal is maintained to 24 bits, but only the top 16 bits are used. This scaling technique results in a
more usable (less sensitive) range of coefficient ki values. The 16 bits are right-shifted eight positions and
multiplied by filter coefficient ki to form the term which contributes to the motor control output. The absolute
magnitude of this product is compared to coefficient il, and the lesser, appropriately signed magnitude then
contributes to the motor control signal.
The derivative signal is multiplied by coefficient kd each derivative sampling interval. This product contributes to
the motor control output every sample interval, independent of the user-chosen derivative sampling interval.
The kp, limited ki, and kd product terms are summed to form a 16-bit quantity. Depending on the output mode
(wordsize), either the top 8 or top 12 bits become the motor control output signal.
LM628 READING AND WRITING OPERATIONS
The host processor writes commands to the LM628 via the host I/O port when Port Select (PS ) input (Pin 16) is
logic low. The desired command code is applied to the parallel port line and the Write (WR ) input (Pin 15) is
strobed. The command byte is latched into the LM628 on the rising edge of the WR input. When writing
command bytes it is necessary to first read the status byte and check the state of a flag called the “busy bit” (Bit
0). If the busy bit is logic high, no command write may take place. The busy bit is never high longer than 100 μs,
and typically falls within 15 μs to 25 μs.
The host processor reads the LM628 status byte in a similar manner: by strobing the Read (RD ) input (Pin 13)
when PS (Pin 16) is low; status information remains valid as long as RD is low.
Writing and reading data to/from the LM628 (as opposed to writing commands and reading status) are done with
PS (Pin 16) logic high. These writes and reads are always an integral number (from one to seven) of two-byte
words, with the first byte of each word being the more significant. Each byte requires a write (WR ) or read (RD )
strobe. When transferring data words (byte-pairs), it is necessary to first read the status byte and check the state
of the busy bit. When the busy bit is logic low, the user may then sequentially transfer both bytes comprising a
data word, but the busy bit must again be checked and found to be low before attempting to transfer the next
byte pair (when transferring multiple words). Data transfers are accomplished via LM628-internal interrupts
(which are not nested); the busy bit informs the host processor when the LM628 may not be interrupted for data
transfer (or a command byte). If a command is written when the busy bit is high, the command will be ignored.
The busy bit goes high immediately after writing a command byte, or reading or writing a second byte of data
(See Figure 6 thru Figure 8).
MOTOR OUTPUTS
The LM628 DAC output port can be configured to provide either a latched eight-bit parallel output or a
multiplexed 12-bit output. The 8-bit output can be directly connected to a flow-through (non-input-latching) D/A
converter; the 12-bit output can be easily demultiplexed using an external 6-bit latch and an input-latching 12-bit
D/A converter. The DAC output data is offset-binary coded; the 8-bit code for zero is 80 hex and the 12-bit code
for zero is 800 hex. Values less than these cause a negative torque to be applied to the motor and, conversely,
larger values cause positive motor torque. The LM628, when configured for 12-bit output, provides signals which
control the demultiplexing process. See for details.
The LM629 provides 8-bit, sign and magnitude PWM output signals for directly driving switch-mode motor-drive
amplifiers. Figure 12 shows the format of the PWM magnitude output signal.
12
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Figure 12. PWM Output Signal Format (Sign output (pin 18) not shown)
Table 2. LM628 User Command Set (1) (2) (3) (4)
Command
Type
Description
Hex
Data
Bytes
Note
RESET
Initialize
Reset LM628
00
0
1
PORT8
Initialize
Select 8-Bit Output
05
0
2
PORT12
Initialize
Select 12-Bit Output
06
0
2
DFH
Initialize
Define Home
02
0
1
SIP
Interrupt
Set Index Position
03
0
1
LPEI
Interrupt
Interrupt on Error
1B
2
1
LPES
Interrupt
Stop on Error
1A
2
1
SBPA
Interrupt
Set Breakpoint, Absolute
20
4
1
SBPR
Interrupt
Set Breakpoint, Relative
21
4
1
MSKI
Interrupt
Mask Interrupts
1C
2
1
RSTI
Interrupt
Reset Interrupts
1D
2
1
LFIL
Filter
Load Filter Parameters
1E
2 to 10
1
UDF
Filter
Update Filter
04
0
1
LTRJ
Trajectory
Load Trajectory
1F
2 to 14
1
STT
Trajectory
Start Motion
01
0
3
RDSTAT
Report
Read Status Byte
None
1
1, 4
RDSIGS
Report
Read Signals Register
0C
2
1
RDIP
Report
Read Index Position
09
4
1
RDDP
Report
Read Desired Position
08
4
1
RDRP
Report
Read Real Position
0A
4
1
RDDV
Report
Read Desired Velocity
07
4
1
RDRV
Report
Read Real Velocity
0B
2
1
RDSUM
Report
Read Integration Sum
0D
2
1
(1)
(2)
(3)
(4)
Commands may be executed “On the Fly” during motion.
Commands not applicable to execution during motion.
Command may be executed during motion if acceleration parameter was not changed.
Command needs no code because the command port status-byte read is totally supported by hardware.
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User Command Set
GENERAL
The following paragraphs describe the user command set of the LM628. Some of the commands can be issued
alone and some require a supporting data structure. As examples, the command STT (STarT motion) does not
require additional data; command LFIL (Load FILter parameters) requires additional data (derivative-term
sampling interval and/or filter parameters).
Commands are categorized by function: initialization, interrupt control, filter control, trajectory control, and data
reporting. The commands are listed in Table 2 and described in the following paragraphs. Along with each
command name is its command-byte code, the number of accompanying data bytes that are to be written (or
read), and a comment as to whether the command is executable during motion.
Initialization Commands
The following four LM628 user commands are used primarily to initialize the system for use.
RESET COMMAND: RESET THE LM628
Command Code: 00 Hex
Data Bytes: None
Executable During Motion: Yes
This command (and the hardware reset input, Pin 27) results in setting the following data items to zero: filter
coefficients and their input buffers, trajectory parameters and their input buffers, and the motor control output. A
zero motor control output is a half-scale, offset-binary code: (80 hex for the 8-bit output mode; 800 hex for 12-bit
mode). During reset, the DAC port outputs 800 hex to “zero” a 12-bit DAC and reverts to 80 hex to “zero” an 8-bit
DAC. The command also clears five of the six interrupt masks (only the SBPA/SBPR interrupt is masked), sets
the output port size to 8 bits, and defines the current absolute position as home. Reset, which may be executed
at any time, will be completed in less than 1.5 ms. Also see commands PORT8 and PORT12.
PORT8 COMMAND: SET OUTPUT PORT SIZE TO 8 BITS
Command Code: 05 Hex
Data Bytes: None
Executable During Motion: Not Applicable
The default output port size of the LM628 is 8 bits; so the PORT8 command need not be executed when using
an 8-bit DAC. This command must not be executed when using a 12-bit converter; it will result in erratic,
unpredictable motor behavior. The 8-bit output port size is the required selection when using the LM629, the
PWM-output version of the LM628.
PORT12 COMMAND: SET OUTPUT PORT SIZE TO 12 BITS
Command Code: 06 Hex
Data Bytes: None
Executable During Motion: Not Applicable
When a 12-bit DAC is used, command PORT12 should be issued very early in the initialization process. Because
use of this command is determined by system hardware, there is only one foreseen reason to execute it later: if
the RESET command is issued (because an 8-bit output would then be selected as the default) command
PORT12 should be immediately executed. This command must not be issued when using an 8-bit converter or
the LM629, the PWM-output version of the LM628.
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DFH COMMAND: DEFINE HOME
Command Code: 02 Hex
Data Bytes: None
Executable During Motion: Yes
This command declares the current position as “home”, or absolute position 0 (Zero). If DFH is executed during
motion it will not affect the stopping position of the on-going move unless command STT is also executed.
Interrupt Control Commands
The following seven LM628 user commands are associated with conditions which can be used to interrupt the
host computer. In order for any of the potential interrupt conditions to actually interrupt the host via Pin 17, the
corresponding bit in the interrupt mask data associated with command MSKI must have been set to logic high
(the non-masked state).
The identity of all interrupts is made known to the host via reading and parsing the status byte. Even if all
interrupts are masked off via command MSKI, the state of each condition is still reflected in the status byte. This
feature facilitates polling the LM628 for status information, as opposed to interrupt driven operation.
SIP COMMAND: SET INDEX POSITION
Command Code: 03 Hex
Data Bytes: None
Executable During Motion: Yes
After this command is executed, the absolute position which corresponds to the occurrence of the next index
pulse input will be recorded in the index register, and bit 3 of the status byte will be set to logic high. The position
is recorded when both encoder-phase inputs and the index pulse input are logic low. This register can then be
read by the user (see description for command RDIP) to facilitate aligning the definition of home position (see
description of command DFH) with an index pulse. The user can also arrange to have the LM628 interrupt the
host to signify that an index pulse has occurred. See the descriptions for commands MSKI and RSTI.
LPEI COMMAND: LOAD POSITION ERROR FOR INTERRUPT
Command Code: 1B Hex
Data Bytes: Two
Data Range: 0000 to 7FFF Hex
Executable During Motion: Yes
An excessive position error (the output of the loop summing junction) can indicate a serious system problem;
e.g., a stalled rotor. Instruction LPEI allows the user to input a threshold for position error detection. Error
detection occurs when the absolute magnitude of the position error exceeds the threshold, which results in bit 5
of the status byte being set to logic high. If it is desired to also stop (turn off) the motor upon detecting excessive
position error, see command LPES, below. The first byte of threshold data written with command LPEI is the
more significant. The user can have the LM628 interrupt the host to signify that an excessive position error has
occurred. See the descriptions for commands MSKI and RSTI.
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LPES COMMAND: LOAD POSITION ERROR FOR STOPPING
Command Code: 1A Hex
Data Bytes: Two
Data Range: 0000 to 7FFF Hex
Executable During Motion: Yes
Instruction LPES is essentially the same as command LPEI above, but adds the feature of turning off the motor
upon detecting excessive position error. The motor drive is not actually switched off, it is set to half-scale, the
offset-binary code for zero. As with command LPEI, bit 5 of the status byte is also set to logic high. The first byte
of threshold data written with command LPES is the more significant. The user can have the LM628 interrupt the
host to signify that an excessive position error has occurred. See the descriptions for commands MSKI and RSTI.
SBPA COMMAND:
Command Code: 20 Hex
Data Bytes: Four
Data Range: C0000000 to 3FFFFFFF Hex
Executable During Motion: Yes
This command enables the user to set a breakpoint in terms of absolute position. Bit 6 of the status byte is set to
logic high when the breakpoint position is reached. This condition is useful for signaling trajectory and/or filter
parameter updates. The user can also arrange to have the LM628 interrupt the host to signify that a breakpoint
position has been reached. See the descriptions for commands MSKI and RSTI.
SBPR COMMAND:
Command Code: 21 Hex
Data Bytes: Four
Data Range: See Text
Executable During Motion: Yes
This command enables the user to set a breakpoint in terms of relative position. As with command SBPA, bit 6 of
the status byte is set to logic high when the breakpoint position (relative to the current commanded target
position) is reached. The relative breakpoint input value must be such that when this value is added to the target
position the result remains within the absolute position range of the system (C0000000 to 3FFFFFFF hex). This
condition is useful for signaling trajectory and/or filter parameter updates. The user can also arrange to have the
LM628 interrupt the host to signify that a breakpoint position has been reached. See the descriptions for
commands MSKI and RSTI.
MSKI COMMAND: MASK INTERRUPTS
Command Code: 1C Hex
Data Bytes: Two
Data Range: See Text
Executable During Motion: Yes
The MSKI command lets the user determine which potential interrupt condition(s) will interrupt the host. Bits 1
through 6 of the status byte are indicators of the six conditions which are candidates for host interrupt(s). When
interrupted, the host then reads the status byte to learn which condition(s) occurred. Note that the MSKI
command is immediately followed by two data bytes. Bits 1 through 6 of the second (less significant) byte written
determine the masked/unmasked status of each potential interrupt. Any zero(s) in this 6-bit field will mask the
corresponding interrupt(s); any one(s) enable the interrupt(s). Other bits comprising the two bytes have no effect.
The mask controls only the host interrupt process; reading the status byte will still reflect the actual conditions
independent of the mask byte. See Table 3.
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Table 3. Mask and Reset Bit Allocations for Interrupts
Bit Position
Function
Bits 15 thru 7
Not Used
Bit 6
Breakpoint Interrupt
Bit 5
Position-Error Interrupt
Bit 4
Wrap-Around Interrupt
Bit 3
Index-Pulse Interrupt
Bit 2
Trajectory-Complete Interrupt
Bit 1
Command-Error Interrupt
Bit 0
Not Used
RSTI COMMAND: RESET INTERRUPTS
Command Code: 1D Hex
Data Bytes: Two
Data Range: See Text
Executable During Motion: Yes
When one of the potential interrupt conditions of Table 3 occurs, command RSTI is used to reset the
corresponding interrupt flag bit in the status byte. The host may reset one or all flag bits. Resetting them one at a
time allows the host to service them one at a time according to a priority programmed by the user. As in the
MSKI command, bits 1 through 6 of the second (less significant) byte correspond to the potential interrupt
conditions shown in Table 3. Also see description of RDSTAT command. Any zero(s) in this 6-bit field reset the
corresponding interrupt(s). The remaining bits have no effect.
Filter Control Commands
The following two LM628 user commands are used for setting the derivative-term sampling interval, for adjusting
the filter parameters as required to tune the system, and to control the timing of these system changes.
LFIL COMMAND: LOAD FILTER PARAMETERS
Command Code: 1E Hex
Data Bytes: Two to Ten
Data Ranges…
Filter Control Word: See Text
Filter Coefficients: 0000 to 7FFF Hex (Pos Only)
Integration Limit: 0000 to 7FFF Hex (Pos Only)
Executable During Motion: Yes
The filter parameters (coefficients) which are written to the LM628 to control loop compensation are: kp, ki, kd,
and il (integration limit). The integration limit (il) constrains the contribution of the integration term
(2)
(see Equation 1) to values equal to or less than a user-defined maximum value; this capability minimizes integral
or reset “wind-up” (an overshooting effect of the integral action). The positive-only input value is compared to the
absolute magnitude of the integration term; when the magnitude of integration term value exceeds il, the il value
(with appropriate sign) is substituted for the integration term value.
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The derivative-term sampling interval is also programmable via this command. After writing the command code,
the first two data bytes that are written specify the derivative-term sampling interval and which of the four filter
parameters is/are to be written via any forthcoming data bytes. The first byte written is the more significant. Thus
the two data bytes constitute a filter control word that informs the LM628 as to the nature and number of any
following data bytes. See Table 4.
Table 4. Filter Control word Bit Allocation
Bit Position
Function
Bit 15
Derivative Sampling Interval Bit 7
Bit 14
Derivative Sampling Interval Bit 6
Bit 13
Derivative Sampling Interval Bit 5
Bit 12
Derivative Sampling Interval Bit 4
Bit 11
Derivative Sampling Interval Bit 3
Bit 10
Derivative Sampling Interval Bit 2
Bit 9
Derivative Sampling Interval Bit 1
Bit 8
Derivative Sampling Interval Bit 0
Bit 7
Not Used
Bit 6
Not Used
Bit 5
Not Used
Bit 4
Not Used
Bit 3
Loading kp Data
Bit 2
Loading ki Data
Bit 1
Loading kd Data
Bit 0
Loading il Data
Bits 8 through 15 select the derivative-term sampling interval. See Table 5. The user must locally save and
restore these bits during successive writes of the filter control word.
Bits 4 through 7 of the filter control word are not used.
Bits 0 to 3 inform the LM628 as to whether any or all of the filter parameters are about to be written. The user
may choose to update any or all (or none) of the filter parameters. Those chosen for updating are so indicated by
logic one(s) in the corresponding bit position(s) of the filter control word.
The data bytes specified by and immediately following the filter control word are written in pairs to comprise 16bit words. The order of sending the data words to the LM628 corresponds to the descending order shown in the
above description of the filter control word; i.e., beginning with kp, then ki, kd and il. The first byte of each word is
the more-significant byte. Prior to writing a word (byte pair) it is necessary to check the busy bit in the status byte
for readiness. The required data is written to the primary buffers of a double-buffered scheme by the above
described operations; it is not transferred to the secondary (working) registers until the UDF command is
executed. This fact can be used advantageously; the user can input numerous data ahead of their actual use.
This simple pipeline effect can relieve potential host computer data communications bottlenecks, and facilitates
easier synchronization of multiple-axis controls.
UDF COMMAND: UPDATE FILTER
Command Code: 04 Hex
Data Bytes: None
Executable During Motion: Yes
The UDF command is used to update the filter parameters, the specifics of which have been programmed via the
LFIL command. Any or all parameters (derivative-term sampling interval, kp, ki, kd, and/or il) may be changed by
the appropriate command(s), but command UDF must be executed to affect the change in filter tuning. Filter
updating is synchronized with the calculations to eliminate erratic or spurious behavior.
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Trajectory Control Commands
The following two LM628 user commands are used for setting the trajectory control parameters (position,
velocity, acceleration), mode of operation (position or velocity), and direction (velocity mode only) as required to
describe a desired motion or to select the mode of a manually directed stop, and to control the timing of these
system changes.
LTRJ COMMAND: LOAD TRAJECTORY PARAMETERS
Command Code:
1F Hex
Data Bytes:
Two to Fourteen
Data Ranges…
Trajectory Control
Word:
Executable During
See Text
Position:
C0000000 to 3FFFFFFF Hex
Velocity:
00000000 to 3FFFFFFF Hex
(Pos Only)
Acceleration:
00000000 to 3FFFFFFF Hex
(Pos Only)
Motion:
Conditionally, See Text
Table 5. Derivative-Term Sampling Interval Selection Codes
Bit Position
thru
Selected Derivative
15
14
13
12
11
10
9
8
0
0
0
0
0
0
0
0
256 μs
Sampling Interval
0
0
0
0
0
0
0
1
512 μs
0
0
0
0
0
0
1
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
768 μs
1024 μs, etc…
65,536 μs
The trajectory control parameters which are written to the LM628 to control motion are: acceleration, velocity,
and position. In addition, indications as to whether these three parameters are to be considered as absolute or
relative inputs, selection of velocity mode and direction, and manual stopping mode selection and execution are
programmable via this command. After writing the command code, the first two data bytes that are written specify
which parameter(s) is/are being changed. The first byte written is the more significant. Thus the two data bytes
constitute a trajectory control word that informs the LM628 as to the nature and number of any following data
bytes. See Table 6.
Table 6. Trajectory Control Word Bit Allocation
Bit Position
Function
Bit 15
Not Used
Bit 14
Not Used
Bit 13
Not Used
Bit 12
Forward Direction (Velocity Mode Only)
Bit 11
Velocity Mode
Bit 10
Stop Smoothly (Decelerate as Programmed)
Bit 9
Stop Abruptly (Maximum Deceleration)
Bit 8
Turn Off Motor (Output Zero Drive)
Bit 7
Not Used
Bit 6
Not Used
Bit 5
Acceleration Will Be Loaded
Bit 4
Acceleration Data Is Relative
Bit 3
Velocity Will Be Loaded
Bit 2
Velocity Data Is Relative
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Table 6. Trajectory Control Word Bit Allocation (continued)
Bit Position
Function
Bit 1
Position Will Be Loaded
Bit 0
Position Data Is Relative
Bit 12 determines the motor direction when in the velocity mode. A logic one indicates forward direction. This bit
has no effect when in position mode.
Bit 11 determines whether the LM628 operates in velocity mode (Bit 11 logic one) or position mode (Bit 11 logic
zero).
Bits 8 through 10 are used to select the method of manually stopping the motor. These bits are not provided for
one to merely specify the desired mode of stopping, in position mode operations, normal stopping is always
smooth and occurs automatically at the end of the specified trajectory. Under exceptional circumstances it may
be desired to manually intervene with the trajectory generation process to affect a premature stop. In velocity
mode operations, however, the normal means of stopping is via bits 8 through 10 (usually bit 10). Bit 8 is set to
logic one to stop the motor by turning off motor drive output (outputting the appropriate offset-binary code to
apply zero drive to the motor); bit 9 is set to one to stop the motor abruptly (at maximum available acceleration,
by setting the target position equal to the current position); and bit 10 is set to one to stop the motor smoothly by
using the current user-programmed acceleration value. Bits 8 through 10 are to be used exclusively; only one bit
should be a logic one at any time.
Bits 0 through 5 inform the LM628 as to whether any or all of the trajectory controlling parameters are about to
be written, and whether the data should be interpreted as absolute or relative. The user may choose to update
any or all (or none) of the trajectory parameters. Those chosen for updating are so indicated by logic one(s) in
the corresponding bit position(s). Any parameter may be changed while the motor is in motion; however, if
acceleration is changed then the next STT command must not be issued until the LM628 has completed the
current move or has been manually stopped.
The data bytes specified by and immediately following the trajectory control word are written in pairs which
comprise 16-bit words. Each data item (parameter) requires two 16-bit words; the word and byte order is most-toleast significant. The order of sending the parameters to the LM628 corresponds to the descending order shown
in the above description of the trajectory control word; i.e., beginning with acceleration, then velocity, and finally
position.
Acceleration and velocity are 32 bits, positive only, but range only from 0 (00000000 hex) to [230]−1 (3FFFFFFF
hex). The bottom 16 bits of both acceleration and velocity are scaled as fractional data; therefore, the leastsignificant integer data bit for these parameters is bit 16 (where the bits are numbered 0 through 31). To
determine the coding for a given velocity, for example, one multiplies the desired velocity (in counts per sample
interval) times 65,536 and converts the result to binary. The units of acceleration are counts per sample per
sample. The value loaded for acceleration must not exceed the value loaded for velocity. Position is a signed,
32-bit integer, but ranges only from −[230] (C0000000 hex) to [230]−1 (3FFFFFFF Hex).
The required data is written to the primary buffers of a double-buffered scheme by the above described
operations; it is not transferred to the secondary (working) registers until the STT command is executed. This fact
can be used advantageously; the user can input numerous data ahead of their actual use. This simple pipeline
effect can relieve potential host computer data communications bottlenecks, and facilitates easier
synchronization of multiple-axis controls.
STT COMMAND: START MOTION CONTROL
Command Code: 01 Hex
Data Bytes: None
Executable During Motion: Yes, if acceleration has not been changed
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The STT command is used to execute the desired trajectory, the specifics of which have been programmed via
the LTRJ command. Synchronization of multi-axis control (to within one sample interval) can be arranged by
loading the required trajectory parameters for each (and every) axis and then simultaneously issuing a single
STT command to all axes. This command may be executed at any time, unless the acceleration value has been
changed and a trajectory has not been completed or the motor has not been manually stopped. If STT is issued
during motion and acceleration has been changed, a command error interrupt will be generated and the
command will be ignored.
Data Reporting Commands
The following seven LM628 user commands are used to obtain data from various registers in the LM628. Status,
position, and velocity information are reported. With the exception of RDSTAT, the data is read from the LM628
data port after first writing the corresponding command to the command port.
RDSTAT COMMAND: READ STATUS BYTE
Command Code: None
Byte Read: One
Data Range: See Text
Executable During Motion: Yes
The RDSTAT command is really not a command, but is listed with the other commands because it is used very
frequently to control communications with the host computer. There is no identification code; it is directly
supported by the hardware and may be executed at any time. The single-byte status read is selected by placing
CS , PS and RD at logic zero. See Table 7.
Table 7. Status Byte Bit Allocation
Bit Position
Function
Bit 7
Motor Off
Bit 6
Breakpoint Reached [Interrupt]
Bit 5
Excessive Position Error [Interrupt]
Bit 4
Wraparound Occurred [Interrupt]
Bit 3
Index Pulse Observed [Interrupt]
Bit 2
Trajectory Complete [Interrupt]
Bit 1
Command Error [Interrupt]
Bit 0
Busy Bit
Bit 7, the motor-off flag, is set to logic one when the motor drive output is off (at the half-scale, offset-binary code
for zero). The motor is turned off by any of the following conditions: power-up reset, command RESET, excessive
position error (if command LPES had been executed), or when command LTRJ is used to manually stop the
motor via turning the motor off. Note that when bit 7 is set in conjunction with command LTRJ for producing a
manual, motor-off stop, the actual setting of bit 7 does not occur until command STT is issued to affect the stop.
Bit 7 is cleared by command STT, except as described in the previous sentence.
Bit 6, the breakpoint-reached interrupt flag, is set to logic one when the position breakpoint loaded via command
SBPA or SBPR has been exceeded. The flag is functional independent of the host interrupt mask status. Bit 6 is
cleared via command RSTI.
Bit 5, the excessive-position-error interrupt flag, is set to logic one when a position-error interrupt condition exists.
This occurs when the error threshold loaded via command LPEI or LPES has been exceeded. The flag is
functional independent of the host interrupt mask status. Bit 5 is cleared via command RSTI.
Bit 4, the wraparound interrupt flag, is set to logic one when a numerical “wraparound” has occurred. To
“wraparound” means to exceed the position address space of the LM628, which could occur during velocity
mode operation. If a wraparound has occurred, then position information will be in error and this interrupt helps
the user to ensure position data integrity. The flag is functional independent of the host interrupt mask status. Bit
4 is cleared via command RSTI.
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Bit 3, the index-pulse acquired interrupt flag, is set to logic one when an index pulse has occurred (if command
SIP had been executed) and indicates that the index position register has been updated. The flag is functional
independent of the host interrupt mask status. Bit 3 is cleared by command RSTI.
Bit 2, the trajectory complete interrupt flag, is set to logic one when the trajectory programmed by the LTRJ
command and initiated by the STT command has been completed. Because of overshoot or a limiting condition
(such as commanding the velocity to be higher than the motor can achieve), the motor may not yet be at the final
commanded position. This bit is the logical OR of bits 7 and 10 of the Signals Register, see command RDSIGS
below. The flag functions independently of the host interrupt mask status. Bit 2 is cleared via command RSTI.
Bit 1, the command-error interrupt flag, is set to logic one when the user attempts to read data when a write was
appropriate (or vice versa). The flag is functional independent of the host interrupt mask status. Bit 1 is cleared
via command RSTI.
Bit 0, the busy flag, is frequently tested by the user (via the host computer program) to determine the busy/ready
status prior to writing and reading any data. Such writes and reads may be executed only when bit 0 is logic zero
(not busy). Any command or data writes when the busy bit is high will be ignored. Any data reads when the busy
bit is high will read the current contents of the I/O port buffers, not the data expected by the host. Such reads or
writes (with the busy bit high) will not generate a command-error interrupt.
RDSIGS COMMAND: READ SIGNALS REGISTER
Command Code: 0C Hex
Bytes Read: Two
Data Range: See Text
Executable During Motion: Yes
The LM628 internal “signals” register may be read using this command. The first byte read is the more
significant. The less significant byte of this register (with the exception of bit 0) duplicates the status byte. See
Table 8.
Table 8. Signals Register Bit Allocation
Bit Position
Function
Bit 15
Host Interrupt
Bit 14
Acceleration Loaded (But Not Updated)
Bit 13
UDF Executed (But Filter Not yet Updated)
Bit 12
Forward Direction
Bit 11
Velocity Mode
Bit 10
On Target
Bit 9
Turn Off upon Excessive Position Error
Bit 8
Eight-Bit Output Mode
Bit 7
Motor Off
Bit 6
Breakpoint Reached [Interrupt]
Bit 5
Excessive Position Error [Interrupt]
Bit 4
Wraparound Occurred [Interrupt]
Bit 3
Index Pulse Acquired [Interrupt]
Bit 2
Trajectory Complete [Interrupt]
Bit 1
Command Error [Interrupt]
Bit 0
Acquire Next Index (SIP Executed)
Bit 15, the host interrupt flag, is set to logic one when the host interrupt output (Pin 17) is logic one. Pin 17 is set
to logic one when any of the six host interrupt conditions occur (if the corresponding interrupt has not been
masked). Bit 15 (and Pin 17) are cleared via command RSTI.
Bit 14, the acceleration-loaded flag, is set to logic one when acceleration data is written to the LM628. Bit 14 is
cleared by the STT command.
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Bit 13, the UDF-executed flag, is set to logic one when the UDF command is executed. Because bit 13 is cleared
at the end of the sampling interval in which it has been set, this signal is very short-lived and probably not very
profitable for monitoring.
Bit 12, the forward direction flag, is meaningful only when the LM628 is in velocity mode. The bit is set to logic
one to indicate that the desired direction of motion is “forward”; zero indicates “reverse” direction. Bit 12 is set
and cleared via command LTRJ. The actual setting and clearing of bit 12 does not occur until command STT is
executed.
Bit 11, the velocity mode flag, is set to logic one to indicate that the user has selected (via command LTRJ)
velocity mode. Bit 11 is cleared when position mode is selected (via command LTRJ). The actual setting and
clearing of bit 11 does not occur until command STT is executed.
Bit 10, the on-target flag, is set to logic one when the trajectory generator has completed its functions for the lastissued STT command. Bit 10 is cleared by the next STT command.
Bit 9, the turn-off on-error flag, is set to logic one when command LPES is executed. Bit 9 is cleared by
command LPEI.
Bit 8, the 8-bit output flag, is set to logic one when the LM628 is reset, or when command PORT8 is executed.
Bit 8 is cleared by command PORT12.
Bits 0 through 7 replicate the status byte (see Table 7), with the exception of bit 0. Bit 0, the acquire next index
flag, is set to logic one when command SIP is executed; it then remains set until the next index pulse occurs.
RDIP COMMAND: READ INDEX POSITION
Command Code: 09 Hex
Bytes Read: Four
Data Range: C0000000 to 3FFFFFFF Hex
Executable During Motion: Yes
This command reads the position recorded in the index register. Reading the index register can be part of a
system error checking scheme. Whenever the SIP command is executed, the new index position minus the old
index position, divided by the incremental encoder resolution (encoder lines times four), should always be an
integral number. The RDIP command facilitates acquiring these data for host-based calculations. The command
can also be used to identify/verify home or some other special position. The bytes are read in most-to-least
significant order.
RDDP COMMAND: READ DESIRED POSITION
Command Code: 08 Hex
Bytes Read: Four
Data Range: C0000000 to 3FFFFFFF Hex
Executable During Motion: Yes
This command reads the instantaneous desired (current temporal ) position output of the profile generator. This
is the “setpoint” input to the position-loop summing junction. The bytes are read in most-to-least significant order.
RDRP COMMAND: READ REAL POSITION
Command Code: 0A Hex
Bytes Read: Four
Data Range: C0000000 to 3FFFFFFF Hex
Executable During Motion: Yes
This command reads the current actual position of the motor. This is the feedback input to the loop summing
junction. The bytes are read in most-to-least significant order.
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RDDV COMMAND: READ DESIRED VELOCITY
Command Code: 07 Hex
Bytes Read: Four
Data Range: C0000001 to 3FFFFFFF
Executable During Motion: Yes
This command reads the integer and fractional portions of the instantaneous desired (current temporal ) velocity,
as used to generate the desired position profile. The bytes are read in most-to-least significant order. The value
read is properly scaled for numerical comparison with the user-supplied (commanded) velocity; however,
because the two least-significant bytes represent fractional velocity, only the two most-significant bytes are
appropriate for comparison with the data obtained via command RDRV (see below). Also note that, although the
velocity input data is constrained to positive numbers (see command LTRJ), the data returned by command
RDDV represents a signed quantity where negative numbers represent operation in the reverse direction.
RDRV COMMAND: READ REAL VELOCITY
Command Code: 0B Hex
Bytes Read: Two
Data Range: C000 to 3FFF Hex, See Text
Executable During Motion: Yes
This command reads the integer portion of the instantaneous actual velocity of the motor. The internally
maintained fractional portion of velocity is not reported because the reported data is derived by reading the
incremental encoder, which produces only integer data. For comparison with the result obtained by executing
command RDDV (or the user-supplied input value), the value returned by command RDRV must be multiplied by
216 (shifted left 16 bit positions). Also, as with command RDDV above, data returned by command RDRV is a
signed quantity, with negative values representing reverse-direction motion.
RDSUM COMMAND: READ INTEGRATION-TERM SUMMATION VALUE
Command Code: 0D Hex
Bytes Read: Two
Data Range: 00000 Hex to ± the Current Value of the Integration Limit
Executable During Motion: Yes
This command reads the value to which the integration term has accumulated. The ability to read this value may
be helpful in initially or adaptively tuning the system.
Typical Applications
PROGRAMMING LM628 HOST HANDSHAKING (INTERRUPTS)
A few words regarding the LM628 host handshaking will be helpful to the system programmer. As indicated in
various portions of the above text, the LM628 handshakes with the host computer in two ways: via the host
interrupt output (Pin 17), or via polling the status byte for “interrupt” conditions. When the hardwired interrupt is
used, the status byte is also read and parsed to determine which of six possible conditions caused the interrupt.
When using the hardwired interrupt it is very important that the host interrupt service routine does not interfere
with a command sequence which might have been in progress when the interrupt occurred. If the host interrupt
service routine were to issue a command to the LM628 while it is in the middle of an ongoing command
sequence, the ongoing command will be aborted (which could be detrimental to the application).
Two approaches exist for avoiding this problem. If one is using hardwired interrupts, they should be disabled at
the host prior to issuing any LM628 command sequence, and re-enabled after each command sequence. The
second approach is to avoid hardwired interrupts and poll the LM628 status byte for “interrupt” status. The status
byte always reflects the interrupt-condition status, independent of whether or not the interrupts have been
masked.
24
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TYPICAL HOST COMPUTER/PROCESSOR INTERFACE
The LM628 is interfaced with the host computer/processor via an 8-bit parallel bus. Figure 13 shows such an
interface and a minimum system configuration.
As shown in Figure 13, the LM628 interfaces with the host data, address and control lines. The address lines are
decoded to generate the LM628 CS input; the host address LSB directly drives the LM628 PS input. Figure 13
also shows an 8-bit DAC and an LM12 Power Op Amp interfaced to the LM628.
LM628 AND HIGH PERFORMANCE CONTROLLER (HPC) INTERFACE
Figure 14 shows the LM628 interfaced to a HPC High Performance Controller. The delay and logic associated
with the WR line is used to effectively increase the write-data hold time of the HPC (as seen at the LM628) by
causing the WR pulse to rise early. Note that the HPC CK2 output provides the clock for the LM628. The
74LS245 is used to decrease the read-data hold time, which is necessary when interfacing to fast host busses.
INTERFACING A 12-BIT DAC
Figure 15 illustrates use of a 12-bit DAC with the LM628. The 74LS378 hex gated-D flip-flop and an inverter
demultiplex the 12-bit output. DAC offset must be adjusted to minimize DAC linearity and monotonicity errors.
Two methods exist for making this adjustment. If the DAC1210 has been socketed, remove it and temporarily
connect a 15 kΩ resistor between Pins 11 and 13 of the DAC socket (Pins 2 and 6 of the LF356) and adjust the
25 kΩ potentiometer for 0V at Pin 6 of the LF356.
If the DAC is not removable, the second method of adjustment requires that the DAC1210 inputs be presented
an all-zeros code. This can be arranged by commanding the appropriate move via the LM628, but with no
feedback from the system encoder. When the all-zeros code is present, adjust the pot for 0V at Pin 6 of the
LF356.
A MONOLITHIC LINEAR DRIVE USING LM12 POWER OP AMP
Figure 16 shows a motor-drive amplifier built using the LM12 Power Operational Amplifier. This circuit is very
simple and can deliver up to 8A at 30V (using the LM12L/LM12CL). Resistors R1 and R2 should be chosen to
set the gain to provide maximum output voltage consistent with maximum input voltage. This example provides a
gain of 2.2, which allows for amplifier output saturation at ±22V with a ±10V input, assuming power supply
voltages of ±30V. The amplifier gain should not be higher than necessary because the system is non-linear when
saturated, and because gain should be controlled by the LM628. The LM12 can also be configured as a current
driver, see 1987 Linear Databook, Vol. 1, p. 2–280.
TYPICAL PWM MOTOR DRIVE INTERFACES
Figure 17 shows an LM18298 dual full-bridge driver interfaced to the LM629 PWM outputs to provide a switchmode power amplifier for driving small brush/commutator motors.
Incremental Encoder Interface
The incremental (position feedback) encoder interface consists of three lines: Phase A (Pin 2), Phase B (Pin 3),
and Index (Pin 1). The index pulse output is not available on some encoders. The LM628 will work with both
encoder types, but commands SIP and RDIP will not be meaningful without an index pulse (or alternative input
for this input … be sure to tie Pin 1 high if not used).
Some consideration is merited relative to use in high Gaussian-noise environments. If noise is added to the
encoder inputs (either or both inputs) and is such that it is not sustained until the next encoder transition, the
LM628 decoder logic will reject it. Noise that mimics quadrature counts or persists through encoder transitions
must be eliminated by appropriate EMI design.
Simple digital “filtering” schemes merely reduce susceptibility to noise (there will always be noise pulses longer
than the filter can eliminate). Further, any noise filtering scheme reduces decoder bandwidth. In the LM628 it was
decided (since simple filtering does not eliminate the noise problem) to not include a noise filter in favor of
offering maximum possible decoder bandwidth. Attempting to drive encoder signals too long a distance with
simple TTL lines can also be a source of “noise” in the form of signal degradation (poor risetime and/or ringing).
This can also cause a system to lose positional integrity. Probably the most effective countermeasure to noise
induction can be had by using balanced-line drivers and receivers on the encoder inputs. Figure 18 shows
circuitry using the DS26LS31 and DS26LS32.
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Note:
Figure 13. Host Interface and Minimum System Configuration
Figure 14. LM628 and HPC Interface
26
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*DAC offset must be adjusted to minimize DAC linearity and monotonicity errors. See text.
Figure 15. Interfacing a 12-Bit DAC and LM628
Figure 16. Driving a Motor with the LM12 Power Op Amp
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Figure 17. PWM Drive for Brush/Commutator Motors
Figure 18. Typical Balanced-Line Encoder Input Circuit
28
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REVISION HISTORY
Changes from Revision B (March 2013) to Revision C
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 28
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Jul-2019
PACKAGING INFORMATION
Orderable Device
Status
(1)
LM629M-6/NOPB
Package Type Package Pins Package
Drawing
Qty
ACTIVE
SOIC
DW
24
30
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
LM629M-6
(4/5)
LM629M-8
NRND
SOIC
DW
24
30
TBD
Call TI
Call TI
-40 to 85
LM629M-8
LM629M-8/NOPB
ACTIVE
SOIC
DW
24
30
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
LM629M-8
LM629MX-8/NOPB
ACTIVE
SOIC
DW
24
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
-40 to 85
LM629M-8
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
10-Jul-2019
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
23-Sep-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
LM629MX-8/NOPB
Package Package Pins
Type Drawing
SOIC
DW
24
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
1000
330.0
24.4
Pack Materials-Page 1
10.8
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
15.9
3.2
12.0
24.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
23-Sep-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM629MX-8/NOPB
SOIC
DW
24
1000
367.0
367.0
45.0
Pack Materials-Page 2
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