CTI 2572-B / 2500C-2572-B Installation and Operation Manual 88
Command Processing Modes
You can specify how the module command execution is synchronized with the PLC logic by setting the
Command Mode bit in WY4. The Command Mode bit is described in detail later in this appendix. You can
select either coupled mode or uncoupled mode.
Coupled Mode Processing (One Shot)
Coupled Mode provides for tight "handshaking" between the module and the PLC. When the PLC triggers the
command, the module will execute the command only once. The module will then wait for acknowledgment
from the PLC before allowing the command to be triggered again. Coupled mode is useful for initiating
transfers that must be done exactly one time per PLC event (such as Starting the Network Server).
Uncoupled Mode Processing (Enable)
Uncoupled Mode does not require a handshaking sequence from the PLC. When Uncoupled Mode is
selected, the module will read the Command Block when the PLC triggers the command and then execute the
command continuously as long as the command trigger is set. Uncoupled mode is useful for providing
continuous updates of PLC data.
NOTE:
If you make changes to the Command Block, the PLC must clear the command trigger and then
reset it before the new Command Block data will be read.
Command Processing Procedure
Following is the typical procedure used to initiate a module command:
• Set up the Command Block(s) in V memory using your PLC programming software
• Load the command slot(s) with the address of the Command Block(s).
• Set the applicable command trigger and mode bits in WY4.
• Monitor the status of the command processing using WX2.
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