CTI 2572-B / 2500C-2572-B Installation and Operation Manual 91
contains bits that are set by the PLC logic. The Command Status Word is located in WX2 and contains bits that
are set by the module.
Since the PLC can send up to four commands to the module per scan, both the Command Control Word and
the Command Status Word contain four sets of bits, one set for each possible concurrent command. For
example, the first four bits (bits 1-4) in both words relate to command Slot 1, the next four bits (bits 5-8) relate
to command Slot 2, etc.
The four command slots execute commands independently. Thus, an error on one command does not affect
processing on the other commands than happen to be executing at the same time. The command slots can be
triggered at different times or all may be triggered concurrently.
Command Control Word
The Command Control Word contains bits that are set by the PLC logic. The following illustration indicates
how the bits within the word are used.
COMMAND CONTROL WORD (WY4)
Error Acknowledge. The PLC sets this bit to acknowledge the error bit which was set by
the 2572.
Command Mode. The PLC sets this bit to control how the module command execution is
synchronized with the PLC logic:
0 = Uncoupled mode - The 2572-B command processing is not synchronized with the
PLC logic.
1 = Coupled mode - The 2572-B command processing is synchronized with the PLC logic.
Command Trigger. The PLC sets this bit to initiate a command.
Abort Trigger. The PLC sets this bit to abort a command in progress. In most cases, use of
the abort bit is not required, since the command executes to completion, either
successfully or with error.
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