Allen-Bradley Logix5000 Reference Manual page 574

Chapter 17 ASCII Serial Port Instructions (ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT)
If you want to
Determine when the buffer contains
termination characters
Count the characters in the buffer
Clear the buffer
Clear out ASCII Serial Port instructions
that are currently executing or are in the
queue
Obtain the status of the serial port control
lines
Turn on or off the DTR signal
Turn on or off the RTS signal
Read a fixed number of characters
Read a varying number of characters, up
to and including the first set of
termination characters
Send characters and automatically
append one or two additional characters
to mark the end of the data
Send characters
574
For example
Check for data that contains termination
characters
Check for the required number of
characters before reading the buffer
·Remove old data from the buffer at
start-up.
·Synchronize the buffer with a device.
Cause a modem to hang up
Read data from a device that sends the
same number of characters each
transmission
Read data from a device that sends a
varying number of characters each
transmission
Send messages that always use the same
termination character(s)
Send messages that use a variety of
termination characters
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Use this Available in these
instruction languages
ABL Relay ladder
Structured text
ACB Relay ladder
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ACL Relay ladder
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AHL Relay ladder
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ARD Relay ladder
Structured text
ARL Relay ladder
Structured text
AWA Relay ladder
Structured text
AWT Relay ladder
Structured text
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