Channel Setup. Allen-Bradley DL4500, micrologix 1500, PLC-5, SLC 500, 1784-u2dhp, DataLink DL, RSLogix5000, KF3, MicroLogix 1200, KF2
Below you will find brief information for DF1 Driver Micrologix 1200, DF1 Driver Micrologix 1500, DF1 Driver SLC 500, DF1 Driver PLC-5, DF1 Driver RSLogix5000.
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Allen-Bradley DF1 Driver
Channel Setup
Supported Link Protocols
Allen-Bradley DF1 Full-Duplex (point-to-point communication)
Allen-Bradley DF1 Half-Duplex Master (multi-drop communication) also known as Allen-Bradley DF1 Polled-
Mode.*
Allen-Bradley DF1 Radio Modem (point-to-point and multi-drop communication).**
*Slave-to-slave communication is not supported.
**Store and forward feature is not supported.
Note: For required firmware versions for Allen-Bradley DF1 Radio Modem support, refer to
.
Channel Properties
General
Serial Communications
Write Optimization
Advanced
Communication Serialization
Link Settings
Channel Properties - General
This server supports the use of simultaneous multiple communications drivers. Each protocol or driver used in a server project is called a channel. A server project may consist of many channels with the same communications driver or with unique communications drivers. A channel acts as the basic building block of an OPC link. This group is used to specify general channel properties, such as the identification attributes and operating mode.
Identification
Name: User-defined identity of this channel. In each server project, each channel name must be unique.
Although names can be up to 256 characters, some client applications have a limited display window when browsing the OPC server's tag space. The channel name is part of the OPC browser information.
For information on reserved characters, refer to "How To... Properly Name a Channel, Device, Tag, and Tag
Group" in the server help.
Description: User-defined information about this channel.
Many of these properties, including Description, have an associated system tag.
Driver: Selected protocol / driver for this channel. This property specifies the device driver that was selected during channel creation. It is a disabled setting in the channel properties.
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Allen-Bradley DF1 Driver
Note: With the server's online full-time operation, these properties can be changed at any time. This includes changing the channel name to prevent clients from registering data with the server. If a client has already acquired an item from the server before the channel name is changed, the items are unaffected. If, after the channel name has been changed, the client application releases the item and attempts to reacquire using the old channel name, the item is not accepted. With this in mind, changes to the properties should not be made once a large client application has been developed. Utilize the User Manager to prevent operators from changing properties and restrict access rights to server features.
Diagnostics
Diagnostics Capture: When enabled, this option makes the channel's diagnostic information available to
OPC applications. Because the server's diagnostic features require a minimal amount of overhead processing, it is recommended that they be utilized when needed and disabled when not. The default is disabled.
Note: This property is disabled if the driver does not support diagnostics.
For more information, refer to "Communication Diagnostics" in the server help.
Channel Properties - Serial Communications
Serial communication properties are available to serial drivers and vary depending on the driver, connection type, and options selected. Below is a superset of the possible properties.
Click to jump to one of the sections:
or
, and
.
Note: With the server's online full-time operation, these properties can be changed at any time. Utilize the User Manager to restrict access rights to server features, as changes made to these properties can temporarily disrupt communications.
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Connection Type
Physical Medium: Choose the type of hardware device for data communications. Options include
COM Port, None, Modem, and Ethernet Encapsulation. The default is COM Port.
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None: Select None to indicate there is no physical connection, which displays the
section.
COM Port: Select Com Port to display and configure the
section.
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Allen-Bradley DF1 Driver l l
Modem: Select Modem if phone lines are used for communications, which are configured in the
section.
Ethernet Encap.: Select if Ethernet Encapsulation is used for communications, which displays the
section.
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Shared: Verify the connection is correctly identified as sharing the current configuration with another channel. This is a read-only property.
Serial Port Settings
COM ID: Specify the Communications ID to be used when communicating with devices assigned to the channel. The valid range is 1 to 9991 to 16. The default is 1.
Baud Rate: Specify the baud rate to be used to configure the selected communications port.
Data Bits: Specify the number of data bits per data word. Options include 5, 6, 7, or 8.
Parity: Specify the type of parity for the data. Options include Odd, Even, or None.
Stop Bits: Specify the number of stop bits per data word. Options include 1 or 2.
Flow Control: Select how the RTS and DTR control lines are utilized. Flow control is required to communicate with some serial devices. Options are: l l
None: This option does not toggle or assert control lines.
DTR: This option asserts the DTR line when the communications port is opened and remains on.
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RTS: This option specifies that the RTS line is high if bytes are available for transmission. After all buffered bytes have been sent, the RTS line is low. This is normally used with RS232/RS485 converter hardware.
RTS, DTR: This option is a combination of DTR and RTS.
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RTS Always: This option asserts the RTS line when the communication port is opened and remains on.
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RTS Manual: This option asserts the RTS line based on the timing properties entered for RTS Line
Control. It is only available when the driver supports manual RTS line control (or when the properties are shared and at least one of the channels belongs to a driver that provides this support).
RTS Manual adds an RTS Line Control property with options as follows: l
Raise: This property specifies the amount of time that the RTS line is raised prior to data transmission. The valid range is 0 to 9999 milliseconds. The default is 10 milliseconds.
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Drop: This property specifies the amount of time that the RTS line remains high after data transmission. The valid range is 0 to 9999 milliseconds. The default is 10 milliseconds.
Poll Delay: This property specifies the amount of time that polling for communications is delayed. The valid range is 0 to 9999. The default is 10 milliseconds.
Tip: When using two-wire RS-485, "echoes" may occur on the communication lines. Since this communication does not support echo suppression, it is recommended that echoes be disabled or a RS-485 converter be used.
Operational Behavior
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Allen-Bradley DF1 Driver l l l
Report Comm. Errors: Enable or disable reporting of low-level communications errors. When enabled, low-level errors are posted to the Event Log as they occur. When disabled, these same errors are not posted even though normal request failures are. The default is Enable.
Close Idle Connection: Choose to close the connection when there are no longer any tags being referenced by a client on the channel. The default is Enable.
Idle Time to Close: Specify the amount of time that the server waits once all tags have been removed before closing the COM port. The default is 15 seconds.
Ethernet Settings
Ethernet Encapsulation provides communication with serial devices connected to terminal servers on the
Ethernet network. A terminal server is essentially a virtual serial port that converts TCP/IP messages on the
Ethernet network to serial data. Once the message has been converted, users can connect standard devices that support serial communications to the terminal server. The terminal server's serial port must be properly configured to match the requirements of the serial device to which it is attached. For more
information, refer to "How To... Use Ethernet Encapsulation" in the server help.
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Network Adapter: Indicate a network adapter to bind for Ethernet devices in this channel. Choose a network adapter to bind to or allow the OS to select the default.
Specific drivers may display additional Ethernet Encapsulation properties. For more information, refer to Channel Properties - Ethernet Encapsulation.
Modem Settings
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Modem: Specify the installed modem to be used for communications.
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Connect Timeout: Specify the amount of time to wait for connections to be established before failing a read or write. The default is 60 seconds.
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Modem Properties: Configure the modem hardware. When clicked, it opens vendor-specific modem properties.
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Auto-Dial: Enables the automatic dialing of entries in the Phonebook. The default is Disable. For
more information, refer to "Modem Auto-Dial" in the server help.
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Report Comm. Errors: Enable or disable reporting of low-level communications errors. When enabled, low-level errors are posted to the Event Log as they occur. When disabled, these same errors are not posted even though normal request failures are. The default is Enable.
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Close Idle Connection: Choose to close the modem connection when there are no longer any tags being referenced by a client on the channel. The default is Enable.
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Idle Time to Close: Specify the amount of time that the server waits once all tags have been removed before closing the modem connection. The default is 15 seconds.
Operation with no Communications
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Read Processing: Select the action to be taken when an explicit device read is requested. Options include Ignore and Fail. Ignore does nothing; Fail provides the client with an update that indicates failure. The default setting is Ignore.
Channel Properties - Write Optimizations
As with any OPC server, writing data to the device may be the application's most important aspect. The server intends to ensure that the data written from the client application gets to the device on time. Given
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Allen-Bradley DF1 Driver this goal, the server provides optimization properties that can be used to meet specific needs or improve application responsiveness.
Write Optimizations
Optimization Method: controls how write data is passed to the underlying communications driver. The options are: l l l
Write All Values for All Tags: This option forces the server to attempt to write every value to the controller. In this mode, the server continues to gather write requests and add them to the server's internal write queue. The server processes the write queue and attempts to empty it by writing data to the device as quickly as possible. This mode ensures that everything written from the client applications is sent to the target device. This mode should be selected if the write operation order or the write item's content must uniquely be seen at the target device.
Write Only Latest Value for Non-Boolean Tags: Many consecutive writes to the same value can accumulate in the write queue due to the time required to actually send the data to the device. If the server updates a write value that has already been placed in the write queue, far fewer writes are needed to reach the same final output value. In this way, no extra writes accumulate in the server's queue. When the user stops moving the slide switch, the value in the device is at the correct value at virtually the same time. As the mode states, any value that is not a Boolean value is updated in the server's internal write queue and sent to the device at the next possible opportunity. This can greatly improve the application performance.
Note: This option does not attempt to optimize writes to Boolean values. It allows users to optimize the operation of HMI data without causing problems with Boolean operations, such as a momentary push button.
Write Only Latest Value for All Tags: This option takes the theory behind the second optimization mode and applies it to all tags. It is especially useful if the application only needs to send the latest value to the device. This mode optimizes all writes by updating the tags currently in the write queue before they are sent. This is the default mode.
Duty Cycle: is used to control the ratio of write to read operations. The ratio is always based on one read for every one to ten writes. The duty cycle is set to ten by default, meaning that ten writes occur for each read operation. Although the application is performing a large number of continuous writes, it must be ensured that read data is still given time to process. A setting of one results in one read operation for every write operation. If there are no write operations to perform, reads are processed continuously. This allows optimization for applications with continuous writes versus a more balanced back and forth data flow.
Note: It is recommended that the application be characterized for compatibility with the write optimization enhancements before being used in a production environment.
Channel Properties - Advanced
This group is used to specify advanced channel properties. Not all drivers support all properties; so the
Advanced group does not appear for those devices.
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Allen-Bradley DF1 Driver
Non-Normalized Float Handling: Non-normalized float handling allows users to specify how a driver handles non-normalized IEEE-754 floating point data. A non-normalized value is defined as Infinity, Not-a-
Number (NaN), or as a Denormalized Number. The default is Replace with Zero. Drivers that have native float handling may default to Unmodified. Descriptions of the options are as follows: l l
Replace with Zero: This option allows a driver to replace non-normalized IEEE-754 floating point values with zero before being transferred to clients.
Unmodified: This option allows a driver to transfer IEEE-754 denormalized, normalized, nonnumber, and infinity values to clients without any conversion or changes.
Note: This property is disabled if the driver does not support floating point values or if it only supports the option that is displayed. According to the channel's float normalization setting, only real-time driver tags
(such as values and arrays) are subject to float normalization. For example, EFM data is not affected by this setting.
For more information on the floating point values, refer to "How To ... Work with Non-Normalized Floating
Point Values" in the server help.
Inter-Device Delay: Specify the amount of time the communications channel waits to send new requests to the next device after data is received from the current device on the same channel. Zero (0) disables the delay.
Note: This property is not available for all drivers, models, and dependent settings.
Channel Properties - Communication Serialization
The server's multi-threading architecture allows channels to communicate with devices in parallel. Although this is efficient, communication can be serialized in cases with physical network restrictions (such as
Ethernet radios). Communication serialization limits communication to one channel at a time within a virtual network.
The term "virtual network" describes a collection of channels and associated devices that use the same pipeline for communications. For example, the pipeline of an Ethernet radio is the master radio. All channels using the same master radio associate with the same virtual network. Channels are allowed to communicate each in turn, in a “round-robin” manner. By default, a channel can process one transaction before handing communications off to another channel. A transaction can include one or more tags. If the controlling channel contains a device that is not responding to a request, the channel cannot release control until the transaction times out. This results in data update delays for the other channels in the virtual network.
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Channel-Level Settings
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Allen-Bradley DF1 Driver
Virtual Network This property specifies the channel's mode of communication serialization. Options include None and Network 1 - Network 50. The default is None. Descriptions of the options are as follows: l
None: This option disables communication serialization for the channel.
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Network 1 - Network 50: This option specifies the virtual network to which the channel is assigned.
Transactions per Cycle This property specifies the number of single blocked/non-blocked read/write transactions that can occur on the channel. When a channel is given the opportunity to communicate, this number of transactions attempted. The valid range is 1 to 99. The default is 1.
Global Settings
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Network Mode: This property is used to control how channel communication is delegated. In Load
Balanced mode, each channel is given the opportunity to communicate in turn, one at a time. In
Priority mode, channels are given the opportunity to communicate according to the following rules
(highest to lowest priority): l
Channels with pending writes have the highest priority.
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Channels with pending explicit reads (through internal plug-ins or external client interfaces) are prioritized based on the read’s priority.
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Scanned reads and other periodic events (driver specific).
The default is Load Balanced and affects all virtual networks and channels.
Devices that rely on unsolicited responses should not be placed in a virtual network. In situations where communications must be serialized, it is recommended that Auto-Demotion be enabled.
Due to differences in the way that drivers read and write data (such as in single, blocked, or non-blocked transactions); the application's Transactions per cycle property may need to be adjusted. When doing so, consider the following factors: l
How many tags must be read from each channel?
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How often is data written to each channel?
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Is the channel using a serial or Ethernet driver?
Does the driver read tags in separate requests, or are multiple tags read in a block?
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Have the device's Timing properties (such as Request timeout and Fail after x successive timeouts) been optimized for the virtual network's communication medium?
Channel Properties - Link Settings
Access Link Settings under channel properties.
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Allen-Bradley DF1 Driver
Station ID: The Station identity number is based on the device being communicated with (excluding radio modems): l l l l
If the destination device is on a DH+ or DH-485 network, communication must go through a Serial-to-
DH+/DH-485 converter (i.e. KF2/KF3 module). In this case, the device being communicated with is the converter, not the destination device itself (which is a Micrologix, SLC500, or PLC-5). The station number for this configuration should be set to the converter's node address.
If the destination device is not on a DH+ or DH-485 network, the device being communicated with is a
Micrologix, SLC500, or PLC-5 PLC. The station number for this configuration can be set to an arbitrary unique address.
If the destination device is on a DH+ or DH-485 converter configuration, Station Number =
Converter's node address (e.g. KF2/KF3 node address).
If the destination device is in a standard serial configuration, the station ID is an rbitrary unique address on the network for the local PC. The range for DH-485 is 1 to 63. Otherwise, the range is 0 to
255.
Link Protocol: The following are the supported link protocols: l l l l
Full-Duplex: (a.k.a Allen-Bradley DF1) used over a point-to-point link, allowing for high performance two-way communications between peers.
Half-Duplex Master: (a.k.a Polled-Mode) is a multi-drop protocol with one master and one or more slaves. For details, see
KF2/KF3 Half-Duplex Master is a multi-drop protocol with one master and one or more slaves that provides lower data throughput than Full Duplex, but adds the ability to communicate with multiple
KF2/KF3 modules from a single COM port. For details, see
Radio Modem: a command/reply protocol with no ACKs or NAKs during the request/response procedure. This reduces the number of bytes the radio modems transmit and receive to complete a transaction. This protocol supports full-duplex communications over a point-to-point link, allowing for high performance two-way communications between peers. It also supports master/slave communications, allowing for multi-drop configurations. Performance exceeds Full-Duplex and Half-
Duplex Protocols.
Slave Poll Delay (ms): The driver is optimized to send master messages and polls as quickly as possible to increase data throughput. The initial slave poll is not delayed because a delay is unnecessary. If the slave needs time to process requests, it is apparent in the initial poll response, so the driver introduces a delay and re-polls the slave. The delay allows the slave time to process the request before the next poll.
Ignore Responses for other Stations: Enable to limit acceptance of responses to those destined for the station indicated in the Station ID field.
Note: Properties and options available vary with options selected.
Half Duplex Master
Half-Duplex Protocol is a multi-drop protocol with one master and one or more slaves. Generally, Half-
Duplex provides lower data throughput than Full Duplex, but it adds the flexibility of being able to communicate with multiple devices from a single COM port. Half-Duplex is a master/slave protocol. In Half-
Duplex Master mode, the driver is the master and all devices on the network are slaves. It is necessary that all the devices on the network be configured as Half-Duplex Slave since only one master is allowed on the network.
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Allen-Bradley DF1 Driver
For more information on configuring the Micrologix/SLC500/PLC5 device using RSLogix, refer to the Rockwell documentation.
Note: If the destination device is on a DH-485 or DH+ network, communication must go through a KF2/KF3 module respectively. If the KF2/KF3 module is configured as a Half-Duplex Slave, the
Link Protocol must be chosen.
Master Responsibilities and Update Rates
The driver (master) is responsible for polling the slaves for data. In general, slaves would be polled in a round-robin manner. Due to the nature of OPC, how often a slave gets polled depends on the slave tags' update rate. In this manner, slaves are only polled when a Read/Write operation is requested from them.
This reduces the traffic on the network and prevents unnecessary requests from taking place. In essence, the design of the client project (specifically update rates assigned) determines the traffic on the network.
The faster the update rate, the more often a slave is polled.
Messages, Sink and Source
There are three messages exchanged between master and slave in a Read/Write operation. The first is the master message requesting the slave to perform a Read/Write operation. The slave does not respond immediately with data as in full-duplex mode. The second message is a poll message from the master to the slave requesting the data gathered from the last master message operation. The third is the slave response with the data requested in the master message. Incoming requests to the slave are placed in what is termed a "sink". Once the slave performs the operation requested, it places the result in what is termed a "source".
Number of Attempts
The number of attempts for master messages and polls share the same number of attempts as configured in the device Retry Attempts. This attempt count is misleading in Half-Duplex mode since there are multiple messages sent from the master in a single data request. For all intents and purposes:
Let cnAttempts = Retry Attempts
# attempts for master message timeout = cnAttempts
# attempts for poll timeout = cnAttempts
# attempts for request timeout = # attempts for master message timeout + # attempts for poll timeout == cnAttempts X 2
Sink and Source Full
Both sink and source are essentially buffers and buffers have limitations. More importantly, it is possible for the sink to fill up with requests. If this occurs, the slave does not acknowledge any master messages it receives. If after cnAttempts the slave does not ACK the master, the slave sink is likely full. The driver then polls the slave emptying any responses the slave may have, making room for responses of the requests that were in the full sink. This polling action takes place until the slave source is empty after cnAttempts. On the next slave request, the sink is likely empty. If it is not, it may mean the driver is polling the slave too quickly. If this is the case, increase the Slave Re-Poll Delay. Likewise, the slave source may also become full and the driver polls the slave until the source is empty after cnAttempts.
Accepted and Discarded Slave Responses
In the above sections, it has been mentioned that the slave is polled until the emptied. This is possible if the slave source is full of queued up responses. On any given poll, only the response to the last master message is accepted, all others are discarded.
Note: Slave-to-slave communication is not supported.
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KF2/KF3 Half Duplex Master
Half-Duplex Protocol is a multi-drop protocol with one master and one or more slaves. Generally, Half-
Duplex provides lower data throughput than Full Duplex, but it adds the flexibility of being able to communicate with multiple KF2/KF3 modules from a single COM port. Half-Duplex is a master/slave protocol. In Half-Duplex Master mode, the driver is the master and all KF2/KF3 modules on the network are slaves. It is necessary that all the devices on the network be configured as Half-Duplex Slave since only one master is allowed on the network.
For more information on configuring the KF2/KF3 module for Half-Duplex slave operation, refer to the
Rockwell documentation.
Master Responsibilities and Update Rates
The driver (master) is responsible for polling the slaves for data. In general, slaves would be polled in a round-robin manner. Due to the nature of OPC, how often a slave gets polled depends on the update rate of the slave’s tags. In this manner, slaves are only polled when a Read/Write operation is requested from them.
This reduces the traffic on the network and prevents unnecessary requests from taking place. In essence, the design of the client project (specifically update rates assigned) determines the traffic on the network.
The faster the update rate, the more often a slave is polled.
Messages, Sink and Source
There are three messages exchanged between master and slave in a Read/Write operation. The first is the master message requesting the slave to perform a Read/Write operation. The slave does not respond immediately with data as in full-duplex mode. The second message is a poll message from the master to the slave requesting the data gathered from the last master message operation. The third is the slave response with the data requested in the master message. Incoming requests to the slave are placed in what is termed a "sink". Once the slave performs the operation requested, it places the result in what is termed a "source".
Number of Attempts
The number of attempts for master messages and polls share the same number of attempts as configured in the device Retry Attempts. This attempt count is misleading in Half-Duplex mode since there are multiple messages sent from the master in a single data request. For all intents and purposes:
Let cnAttempts = Retry Attempts
# attempts for master message timeout = cnAttempts
# attempts for poll timeout = cnAttempts
# attempts for request timeout = # attempts for master message timeout + # attempts for poll timeout == cnAttempts X 2
Sink and Source Full
Both sink and source are essentially buffers and buffers have limitations. More importantly, it is possible for the sink to fill up with requests. If this occurs, the slave does not acknowledge any master messages it receives. If after cnAttempts the slave does not ACK the master, it is most likely the case that the slave sink is full. The driver then polls the slave emptying any responses the slave may have, making room for responses of the requests that were in the full sink. This polling action takes place until the slave source is empty after cnAttempts. On the next slave request, the sink is likely empty. If it is not, it may mean the driver is polling the slave too quickly. If this is the case, increase the Slave Re-Poll Delay. Likewise, the slave source may also become full and the driver again polls the slave until the source is empty after cnAttempts.
Accepted and Discarded Slave Responses
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Allen-Bradley DF1 Driver
In the above sections, it has been mentioned that the slave is polled until the emptied. This is possible if the slave source is full of queued up responses. On any given poll, only the response to the last master message is accepted: all others are discarded.
Note: Slave-to-slave communication is not supported.
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Key features
- Supports Allen-Bradley Micrologix, SLC500, and PLC5 series PLCs
- Reliable communication with Allen-Bradley DF1 devices
- Connects to client applications including HMI, SCADA, Historian, and MES
- Supports full-duplex, half-duplex master, and radio modem communication protocols
- Provides write optimization features for improved performance
- Includes diagnostic capabilities for troubleshooting
- Offers both simulated and real-time device operation modes
- Supports direct connection and DH-485/DH+ networks