Rockwell Automation Allen-Bradley 1769-ASCII, User Manual

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80 Rockwell Automation Publication 1769-UM012B-EN-P - January 2014
Chapter 3 I/O Memory Mapping
Set Up the Receive Delimiters
The receive Start Delimiter is a start-of-string character used by the 1769-ASCII
module to determine that the first expected character from the ASCII device is
received. Upon receipt of this character, the 1769-ASCII module starts storing
the string data in its internal data buffer on the serial receive side.
The receive Stop Delimiter is an end-of-string character used by the 1769-ASCII
module to determine that the last expected character from the ASCII device is
received. Upon receipt of this character the 1769-ASCII module update its
internal data buffer on the serial receive side. The module also makes the new
string available to the CompactBus Master in the Produce buffer.
The receive delimiters can be set to any valid ASCII character that can be
received over the link. Be sure to avoid setting the delimiter to a value outside of
the valid range for your data bits. For example, a data bit size setting of 7 gives you
a delimiter range of 0…127 decimal, 00…7F hexadecimal.
If you do not receive a valid receive delimiter, the device updates the Produce
buffer on detection of a buffer full (overflow) condition only. For example, the
device updates when it receives the number of characters defined in the Max
Number of Receive Characters parameter. The device also updates if a time-out
occurs (if you selected the time-out option).
The Receive Data, Transmit Data Swap, Handshake mode, MSG Timeout, and
Pad Character are all handled per channel on the Advance Configuration tab in
the Add-On Profile.