Omron V550-A20 Operation Manual page 51

V550-A20 Operation Manual
The remainder of this section defines the message formats and timing
requirements for the protocol used on RS-485 multidrop (2-wire) communi-
cations lines. The protocol is defined for both the "master" device and the
"slave" devices. This protocol is defined for a one-master system only. The
following definitions may help you understand this protocol a little better.
ASCII digit: This means the ASCII code for a single decimal digit. For
example, 30h is the ASCII digit that encodes a zero.
HEX digit: This means the ASCII code for a single hexadecimal digit. Some
examples are, 35h is the code for a five, 42h is the code for a "B" (which
equals 11 base 10), the hexadecimal number "5A" would be encoded by the
two HEX digits 35h and 41h.
Message Formats
The standard communications parameters are as follows:
Standard asynchronous data frame (least significant bit first)
7 data bits
1 even parity bit
2 stop bits
If the master can only support 8 bit data plus a parity bit, then the
format is as follows:
8 data bits
1 odd parity bit
1 stop bit
(Odd parity is required to make sure that the guard character will be
all ones with one for parity.)
You can use any baud rate that is supported by both the master and
the slaves. System performance is usually best when using the
highest baud rate possible.
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Section 5-
Appendices
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