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CTI 2572 Installation and Operation Guide
137
Command Abort Timing
There may be rare occasions when you need to abort a command that is in progress. For example, if
you triggered a R
EAD REMOTE command with an infinite timeout and the data was never returned,
the protocol manager would wait forever, blocking further execution in the command slot. Figure 27
illustrates abort timing.
Assume the module is busy
processing a command (Time
A). At time B, the PLC asserts
ABORT TRIG to stop the
ongoing command processing.
When the module recognizes
that ABORT TRIG is high, the
module will assert ABORT
BUSY (Time C).
After detecting ABORT BUSY,
the PLC should clear ABORT
TRIG (Time D). When the
Module has completed abort
processing, it clears ABORT
BUSY(Time E).
After ABORT BUSY is
cleared, the module will clear
CMD BUSY (Time F). Time F
may be on the same scan or on
a later scan than time D.
ABORT BUSY will never be asserted unless CMD BUSY is also asserted.
NOTE:
ABORT BUSY will be cleared even if the ABORT TRIG is still active. If the PLC does not clear
ABORT TRIG, no further commands will be processed for the Command slot.
Depending upon the nature of the command and circumstances of execution, some commands cannot
be aborted.
NOTE:
Setting all four abort triggers and asserting the module reset bit in WY3 will cause the module to
perform a complete reset.
Figure 27. Command Abort Timing