Rockwell Automation Allen-Bradley 1769-ASCII, User Manual

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Rockwell Automation Publication 1769-UM012B-EN-P - January 2014 79
I/O Memory Mapping Chapter 3
Configuration File Parameter
Operation Each channel’s serial port and data string operation is configured individually and
independently. The parameters that are not independent are the Data Buffer
mode and the Transmit and Receive buffer sizes. The sum of the two channels’
buffer sizes cannot total more than 200 bytes, in each direction, while using the
Simultaneous Buffer mode.
Data Buffer Mode
This parameter defines whether the data is in the Alternate mode or
Simultaneous mode on the CompactBus. You can access the Data Buffer mode in
the Module Definition dialog box. Go to the General tab and click Change.
Set Up the Data Frame Format
The data frame format parameter defines the size of the data frame that is
transmitted and received over the serial link. This parameter defines the
following:
•
Number of data bits per character (7 or 8)
•
Parity (odd, even, or none)
•
Number of stop bits (1 or 2)
The 1769-ASCII module provides several options to match the choices available
with your ASCII device because they must match exactly. Frame format can be
handled also in the Add-On Profile on the Configuration tab.
Although the Add-On-Profile lets you select only six options. You can populate
these configuration tags as documented in the following sections.
Receive Delimiter Mode
The Start Delimiter indicates that the module starts storing data received at its
serial port. The End Delimiter signals the end of data to be stored. If you use a
receive delimiter, you can include or exclude the delimiter in the ASCII message
sent to the CompactBus Master. The Start and Stop Delimiters are used and set
independently of each other:
•
If the Start Delimiter is not used, the module receives and stores any valid
characters received after the completion of the previous message.
•
If the Stop Delimiter is not used, the module collects data up to the Max
Receive Characters parameter value.