CTI 2572-A, Installation And Operation Manual

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CTI 2572-A Installation and Operation Guide
102
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
R
EMOTE
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 17
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 17. Command Abort Timing