Publication 1766-RM001A-EN-P - October 2008
362 ASCII Instructions
Instruction Types and
Operation
There are two types of ASCII instructions, ASCII string control and ASCII
port control. The string control instruction type is used for manipulating
data and executes immediately. The port control instruction type is used
for transmitting data and makes use of the ASCII queue. More details are
provided below.
ASCII String Control
These instructions are used to manipulate string data. When a string
control instruction is encountered in a ladder logic program, it executes
immediately. It is never sent to the ASCII queue to wait for execution. The
following table lists the ASCII string control instructions used by the
MicroLogix 1400 controllers:
ASCII Port Control
These instructions use or alter the communication channel for receiving or
transmitting data. All ASCII port control instructions support channel 2, as
well as channel 0. The following table lists the ASCII port control
instructions used by the MicroLogix 1400 controllers:
When the ACL (ASCII Clear Buffer) instruction is encountered in a ladder
logic program, it executes immediately and causes all instructions to be
removed from the ASCII queue, including stopping execution of the ASCII
instruction currently executing. The ER (error) bit is set for each
instruction that is removed from the ASCII queue.
Table 21.1
MicroLogix 1400
ACI (String to Integer) AIC (Integer to String)
ACN (String Concatenate) ASC (String Search)
AEX (String Extract) ASR (ASCII String Compare)
Table 21.2
MicroLogix 1400
ABL (Test Buffer for Line) ARD (ASCII Read Characters)
ACB (Number of Characters in Buffer) ARL (ASCII Read Line)
ACL (ASCII Clear Buffer) AWA (ASCII Write with Append)
AHL (ASCII Handshake Lines) AWT (ASCII Write)
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