Installation manual

Publication 1747-RM001G-EN-P - November 2008
10-2 ASCII Instructions
ASCII Instruction Overview
ASCII instructions are available in SLC 5/03 OS301 and above processors,
and all SLC 5/04 and SLC 5/05 processors. There are two types of ASCII
instructions.
• ASCII port control - these include instructions that use or alter the
communication channel for receiving or transmitting data. When using
these instructions, the system configuration for channel 0 must be set to
“User Mode.”
(ABL, ACB, ACL*, AHL*, ARD, ARL, AWA*, AWT*)
*may be executed in either user or system mode
ASCII port control instructions are queued in the order that they are
scanned and are dependent on one another to execute (except ACL
which executes immediately). For example, if you have an ARD (ASCII
Read instruction) and then an AWT (ASCII Write instruction), the
Done bit or the Error bit of the ARD must be set before the AWT can
begin executing (even if the AWT was enabled while the processor was
executing the ARD). A second ASCII port control instruction cannot
begin executing until the first has completed. However, the processor
does not wait for an ASCII port control instruction to complete before
continuing to execute your ladder program.
• ASCII string control - these include instructions that manipulate string
data. (ACI, ACN, AEX, AIC, ASC, ASR)
ASCII string control instructions execute immediately. They are never
sent to the queue to wait their turn for execution.
Protocol Parameter
Overview
Listed below are the ASCII protocol parameters that you set via the Channel 0
configuration screens in your programming software.
Table 10.2 ASCII Protocol Parameters
Description Specification
Baud Rate Toggles between 110, 300, 600, 1.2K, 2.4K, 4.8K, 9.6K, and
19.2K (additional rate of 38.4K for SLC 5/04 and SLC 5/05
only). The default is 19.2K.
Start Bits The default is 1 and cannot be changed.
Stop Bits Options include 1, 1.5, and 2 The default is 1.
Parity Toggles between None, Odd, and Even. The default is None.