576 Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Chapter 17 ASCII Serial Port Instructions (ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT)
The ASCII queue holds up to 16 instructions. When the queue is full, an
instruction tries to enter the queue on each subsequent scan of the instruction, as
depicted below.
Scan Scan Scan Scan
Enters Queue
Resets status bits.
Executes
When scanned and .DN
or .ER are set, sets the
.EM bit.
In this example,
finds termination
characters.
Rung-condition-in
false true false true false
.EN off on off on off
.EU off on
.RN off on off on off
.DN or .ER off on off on
.FD off on off on
.EM off on off on
Scan Scan Scan Scan
Enters queue
Attempts to enter queue but queue is full
Rung-condition-in
false true false
.EN off on
.EU off on
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