CTI 2572-A, Installation And Operation Manual

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CTI 2572-A Installation and Operation Guide V1.3 47
Note the function of C14 and C15. They are used to detect the fact that a 2572-A command cycle has
completed. Refer to the timing diagram below. The 2572-A will raise the Command Busy it after the
PLC logic sets the command trigger. If there is no error, the 2572-A will lower command busy after
the PLC lowers the command trigger and the 2572-A module has successfully completed the
command. If there is an error, the 2572-A will raise the error bit. In this case, it will not lower the
command busy bit until the PLC sets the error acknowledge bit. When the command busy bit is
lowered, the command cycle is complete and the 2572-A can accept another command in the
command slot.
Please refer to APPENDIX C. PLC COMMAND INTERFACE for detailed information regarding
the timing of the trigger, command busy and command error bits. C14 is used to latch the beginning
of a command cycle. When the command busy bit is lowered after C14 has been set, C15 is set.
When C15 is set, the command cycle has been completed.
Command Busy Bit
Time
C14 is set
here when
Command
Busy bit
comes on
On
C15 is set here
when Command
Busy bit goes off,
after C14 is on,
indicating a
complete
command cycle
Command Error Bit