184 Rockwell Automation Publication 1769-IN088A-EN-P - February 2011
Chapter 3 I/O Memory Mapping
• PA = Parity error. A parity error has occurred with the received data string.
This usually indicates a mismatch in the serial port set-up of the ASCII
device and the Compact module. It could also indicate that noise has
occurred on the line and degraded the signal. This bit is set when the
receive FIFO contains a message in which a parity error occurred in one of
the incoming bytes. This bit is reset when the receive FIFO is emptied or
when a new message is received with no parity error.
• RO = Receive buffer overflow. Some input data has been lost.
• TO = Transmit buffer overflow. Some output data has been lost.
Simultaneous Mode (Two Channels) Output File
Maximum size is shown below. Refer to the Compact I/O 1769-ASCII Module
User Manual, publication 1769-UM012
, to use smaller output files.
Word
Bit Position
1514131211109876543210
Channel 0 Data
0 Reserved Tx Transaction ID
1 Reserved Rx Transaction ID Request
2 Reserved
3 Length (Number of Bytes)
4 Character 1 Character 0
5 Character 3 Character 2
… Character … Character …
x
(1)
(1) X is calculated based on the size of Channel 0 data as specified in the configuration file. Both channels cannot
contain 200 characters as the total configuration file size can be only 108 words.
Last Character Character …
Channel 1 Data
x+1 Reserved Tx Transaction ID
x+2 Reserved Rx Transaction ID Request
x+3 Reserved
x+4 Length (Number of Bytes)
x+5 Character 1 Character 0
x+6 Character 3 Character 2
… Character … Character …
y
(2)
(2) Y is equal to the connection size minus 1, with a maximum value of 107 for a buffer size of 108.
Last Character Character …
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