Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 116)

Chapter 8
Host Commands Using the RS-485 Interface
8–4
The following table lists the status response codes for all of the commands.
Binary Value
Hex
Value
Meaning of Code
00000000 00 Success, No errors.
00010000 10 Valid command, but the format or address is
invalid.
00100000 20 Invalid or unsupported command.
00110000 30 Hardware fault (reserved and unused).
01000000 40 Success, but no data available (read command
only).
10000000 80 Success, but data truncated.
TRANSACTION WORD (Bytes 2 and 3) - This 16 bit message is assigned
by the host and is returned in the reply message from the decoder with the
same value as the command command and status bytes.
LOW-ADDRESS or FUNCTION CODE (Byte 4) - This is an optional
code that allows the host device to send supplemental codes. The meaning of
these codes is dependent upon the COMMAND byte (0):
•
For Read and Write commands, this byte contains the low-byte of a two
byte address.
•
When used with the Diagnostic command, this byte contains the
diagnostic command. Refer to Link Diagnostic Command section.
HI-ADDRESS (Byte 5) - This optional byte specifies the high-byte of a two
byte address when using the Read or Write commands.
DATA (Byte 6 or 4) - This data field is optional and begins at byte 6 or 4.
The length of this data field depends upon whether or not bytes 4 and 5
(Low-Address/Function Code and High-Address) are used:
•
If bytes 4 and 5 are used, the data field begins at byte 6 and may contain
122 bytes.
•
If bytes 4 and 5 are not used, the data field begins at byte 4 and may be
124 bytes long. How the data in this field is used depends upon the
command and optional function code.
PCCC Commands
In the remainder of this chapter, we provide the PCCC commands. The
following commands are available:
•
Unprotected Read Command
•
Unprotected Write Command
•
Communication Link Diagnostic Command