Rockwell Automation 6001-F2E AB STANDARD DRIVER SFTW - Manual (Page 39)

Specifying Message Packet Commands
with Send_StdDrv()
Appendix B
B-2
Communicating with a Token-passing Device (SLC-500 Processor)
Figure B.1 shows the message packet format you use to communicate
with token-passing devices (such as an SLC-500 processor).
Important: Shaded blocks indicate packet fields that may or may not be
included in your message packet, depending on the command.
Figure B.1
Message Packet Format for Communicating with an SLC-500 Processor
LEN TYP DST SRC CMD STS TNS
Data
(from Application Layer)
DATA
FNC ADDR SIZE TNS TNS
Table B.A explains the message packet fields in Figure B.1.
Table B.A
Communicating with an SLC-500 Processor
This Packet Field Is the
LEN length of the message packet (including LEN)
TYP type code identifying this message packet format
(this is always a 0)
DST DH-485 destination address for this packet
SRC DH-485 address of the device sending the packet
CMD command byte
STS message packet status
TNS transaction number (2 bytes)
FNC byte used with CMD. If used, it defines the specific function
under the command type
ADDR two-byte field that contains the address of a memory
location in the command executor where the command is to
begin executing.
SIZE byte that specifies the number of data bytes to be
transferred by a message
DATA data sent as part of themessage command