Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 121)

Chapter 8
Host Commands Using the RS-485 Interface
8–9
You can use the unprotected write command to send configuration
parameters and commands to the decoder. The write command is structured
as follows:
UNPROTECTED WRITE COMMAND
00000000 00001000
TRANSACTION WORD
HI and LOW ADDRESS BYTES
DATA
MAXIMUM OF
122 BYTES
HI Byte LOW Byte
Unprotected Write Command Structure
The following are descriptions of each byte in the command.
COMMAND (Byte 0) - The command byte for an unprotected write
command has the following structure:
0 0 0 0 1 0 0 0
MSB LSB
1000 =
Unprotected
Write Command
Bit #6 Cleared
For Command
Always Set to 0
STATUS (Byte 1) - The status byte is cleared for the command.
TRANSACTION WORD (Bytes 2 & 3) - The transaction word is provided
by the host and is returned by the decoder (exactly as it was sent) in the
reply.
HI and LOW ADDRESS (Bytes 4 & 5) - These bytes specify the area in the
decoder’s memory which are going to be written to. There are two areas of
Unprotected Write Command