Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 126)

Chapter 8
Host Commands Using the RS-485 Interface
8–14
You can obtain diagnostic data on the communications link (RS-485
Local-Area Network) using the diagnostic commands. The diagnostic
command has the following structure:
LINK DIAGNOSTIC COMMAND
00000000 00000110
TRANSACTION WORD
HI Byte LOW Byte
FUNCTION CODE
DIAGNOSTIC LOOP DATA
(Only With Diagnostic Loop Command)
Link Diagnostic Command Structure
The following are descriptions of each byte in the diagnostic link command:
COMMAND (Byte 0) - The command byte for the link diagnostics
command has the following structure:
0 0 0 0 0 1 1 0
MSB LSB
0110 = Link
Diagnostics
Command
Bit #6 Cleared
For Command
Always Set to 0
STATUS (Byte 1)- The status byte is cleared for command.
TRANSACTION WORD (Bytes 2 &3) - As with the other commands the
transaction word is a two byte code that is returned (exactly as it was sent) in
the decoder’s reply message.
Communication Link Diagnostic
Commands