Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 34)

2–5 Understanding DF1 Protocol
Publication 1770Ć6.5.16 - October 1996
Allen-Bradley interface modules send data serially over the
RS-232-C/RS-422-A interface, one 10-bit byte—11-bit byte with
parity—at a time. The transmission format conforms to ANSI
X3.16, CCITT V.4, and ISO 1177 standards, with the exception that
the parity bit is retained while the data length is extended to eight
bits. Make sure that your computer conforms to this mode of
transmission. The transmission format is:
No Parity
start bit
data bit 0
data bit 1
data bit 2
data bit 3
data bit 4
data bit 5
data bit 6
data bit 7
one stop bit
With Parity
start bit
data bit 0
data bit 1
data bit 2
data bit 3
data bit 4
data bit 5
data bit 6
data bit 7
even parity bit
one stop bit
For all DH, DH+, and DH485 interface modules, you must comply
with this transmission format. For communication rates and parity
settings, refer to your module’s user manual.
Character Transmission