Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 84)

6–5 Application Layer Message Packets
Publication 1770Ć6.5.16 - October 1996
CMD and FNC
These bytes work together to define the activity that is to be
performed by the command message at the destination node.
Values for these bytes are supplied by the application layer.
The message format depends on the CMD and FNC values.
command message = 0
reply message = 1
0
Command
or Reply
Priority
Bit: 7 6 5 4 3 2 1 0
0 Command
always = 0 always = 0
normal priority = 0
high priority= 1 ➀
CMD byte
command code
➀ High priority only applies to DH links. It does not apply to DH+, DH485, or DHII links.
This byte Defines the And has these values
CMD
(command)
command type
see table that begins on
FNC
(function)
specific function under that command type
see table that begins on
page 7-2
Example code
PLCĆ2 command Ċ enter download mode
send = 00000111 (07 hex)
reply = 01000111 (47 hex)
highĆpriority send (DH only) = 00100111 27 hex
highĆpriority reply (DH only) = 01100111 (67 hex)