Rockwell Automation 6001-F2E AB STANDARD DRIVER SFTW - Manual (Page 41)

Specifying Message Packet Commands
with Send_StdDrv()
Appendix B
B-4
The message packet fields for the previous applications are described in
more detail in the table below.
Table B.C
Message Packet Field Description
Field Description
LEN This field identifies the length of the message packet (including LEN). The
allowed range is 0-255.
TYP This is the code that identifies the type of communication. Use 0 to
communicate to an SLC-500 processor and 5 to communicate to a
slave-only device.
IMMEDIATE BLOCK The allowed range is 0 and 128-255 (depending on the device.)
DST and SRC The DST (destination) byte contains the DH-485 node number of the
node that is the ultimate destination of the message. The SRC (source)
byte contains the DH-485 node number of the node that originated the
message.
The application layer supplies the DST value; the data link layer supplies
the SRC value. Allowed values for these bytes are 0 to 31 (decimal).
CMD and FNC The CMD (command) and FNC (functions) bytes (1 byte each) together
define the activity to be performed by the command message at the
destination node. Command defines the command type and FNC, if
used, defines the specific function under that command type.
STS and EXT STS The STS (status) and EXT STS (extended status) bytes indicate the
status of the message transmission. In command messages, the
application program should always set the STS value to 0. In reply
messages, the STS byte may contain one of the status codes listed in
appendix D . If the high byte = F0 Hex, there is extended status
information in the EXT STS byte. Otherwise, there is no EXT STS byte.
An STS value of 0 in a reply message means the command has been
executed with no error.
In a reply message, the STS byte is divided between application layer
and link layer. The link layer uses bits 0 through 3 of the STS byte to
report local errors (those errors that occur when the link layer attempts to
transmit a message across the link).
The application layer uses bits 4 through 7 of the STS byte (and in some
cases, the EXT STS byte) to report remote errors (those errors that occur
when the command executor at the destination node tries to execute the
command message). Refer to appendix D for more information.
Message Packet Fields