Rockwell Automation 1775-S5_SR5,D17756.5.5 User Manual PLC-3 FAMILY I/0 - Manual (Page 123)

Diagnostics Methods
Chapter 7
7-11
Important: When the scanner is polling, both the XMTG and RCVG
LEDs trun on. Also, if there is a duplicate node on DH+, the yellow
disable indicator blinks until the condition is removed.
The scanner can send out DH and DH+ diagnostic commands using a
special format of the assignment command. As with other assignment
commands, you can program this command directly into the message
instruction or use it within a DH/DH+ procedure.
ATTENTION: If the diagnostic assignment command is not
properly programmed, unanticipated data can be sent to remote
stations on the DH or DH+ link causing unpredictable
operation.
This assignment command requires that data table be reserved for both the
command to be sent and the response that will be returned from the remote
station. You must reserve a minimum of 126 words of data table for
the response.
The command is formatted as follows (note the special use of the
exclamation point):
$B0:0 = !H023 $B1:0
response block location
destination
command block location
Where: Is the:
response block
location
starting address of the data table address which will be
used to save the response data from the remote station.
destination
remote station address to where this command is being
sent. This address can be any remote station address and
can include a bridge address when using DH+
(for example !H1:2:3).
command block
location
Starting address of the data table address which contains
the command being sent to the remote station.
DH/DH+ Diagnostic
Assignment Command