Rockwell Automation 5370 CVIM Communications Manual - Manual (Page 75)

Chapter 5
Using the RS-232 Ports
5–5
In describing the ASCII Protocol we use the following conventions:
Non–printable ASCII control characters are represented as follows:
[CR] = Carriage Return
[LF] = Line Feed
___ = Space
ASCII commands are provided in large bold characters:
>RR, RB,3 [CR]
Unless _ is specified, there are no spaces between characters. Some
commands have fields which can contain variable data such as number of
times a command is repeated, block numbers, data, etc. These fields are
shown using lowercase lettering:
>W,CBn,d [CR]
In this example, the letters n and d indicate data which is variable. The
other characters indicate fixed data.
After you have made the equipment connections and configured the CVIM
module for RS–232 communications, all ASCII strings generated by the host
will be interpreted as commands. The CVIM module will then validate the
command structure. If the command has an acceptable structure the CVIM
module will reply: [CR][LF]. Refer to Appendix E for an ASCII conversion
chart. If the command has an incorrect structure the CVIM module will
respond: ? [CR] [LF]. The CVIM module will process all validated
commands and discard any invalid commands. Data may or may not be
returned with a command depending upon the type of command that was
sent.
Note: A simple way to test the RS–232 links is to send the CVIM module a
[CR]. If you have the port properly connected and the CVIM module
configured for RS-232, the CVIM module should send a ? [CR][LF] in
response. If no response is provided, check your connections and CVIM
module configuration.
Note: Some commands cause a continuous flow of returned data. To stop the
flow of data you should send another command (valid or invalid). We
recommend using a [CR] to stop the transmission of data.
The CVIM module recognizes the following ASCII characters; all other
characters are ignored.
•
Upper and lowercase letters A through Z (case is insignificant).
ASCII Protocol
Overview
ASCII Character Set