Rockwell Automation Allen-Bradley 1769-ASCII, User Manual

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84 Rockwell Automation Publication 1769-UM012B-EN-P - January 2014
Chapter 3 I/O Memory Mapping
Receive Timeout
The 1769-ASCII module has a receive timeout value configurable in 1 ms
increments. The timeout counter resets on the receipt of each new byte of data. If
the timeout counter expires, the 1769-ASCII module sets the Non-Delimited
flag in the Status Byte and updates the Receive/Produce buffer with the current
data string.
How to Send Data from the
1769-ASCII Module The Consume buffer can include one channel's data or combine both channel's
data in one buffer from the CompactBus Master to the 1769-ASCII module.
If you configure the module to accept only one channel's data in the Consume
buffer, the channel can accept up to 200-bytes of ASCII data. The Consume
buffer contains an 8-byte header followed by the channel’s associated ASCII data.
CNI or CNO are tags names from Generic module - the Add-On-Profile term
for indicating which channel to transmit data is Local:S:O.TxChNumber. Bit = 0
indicates channel 0 and Bit = 1 indicates channel 1.
If the module is configured to accept both channels’ data, the Consume buffer
sends two ASCII buffers each preceded by its associated header. Under this
configuration, the combined length of both channels’ data cannot exceed the
modules 200-byte ASCII buffer limit.
The header contains the Transaction ID of the data in the first byte. This value is
set to 0 at the beginning of communication.
The second byte has the handshaking bits to denote which channel's data is
needed in the subsequent Produce buffers, if configured for single-channel
communication. The third and fourth bytes are length indicators. The ensuing
bytes are the data that you wish to send to the 1769-ASCII module.
IMPORTANT
If you use the Byte-Swap mode, all transaction and receive strings must be
in multiples of 2 bytes.