Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 123)

Chapter 8
Host Commands Using the RS-485 Interface
8–11
0 1 0 0 1 0 0 0
MSB LSB
1000 =
Unprotected
Write
Bit #6 Set to 1
For Reply
Always Set to 0
STATUS (Byte 1) - Table 8.A describes the meaning of the status codes. An
invalid address will return a code of 10 (hex).
TRANSACTION WORD (Bytes 2 & 3) - These two bytes are the same
transaction word that was sent out with the write command.
Writing to the Command Area Memory
Table 8.C lists the areas of memory in the command block of the decoder
that the host can write to. When a specific address of the command block
memory is used in a write command, that specific command will be initiated
by the decoder. For example, to clear all counters the following write
command would be sent:
UNPROTECTED WRITE TO COMMAND AREA OF MEMORY
00000000 00001000
TRANSACTION WORD
HI Byte LOW Byte
00000110 00110001
Note: The address for the Clear All Counters is 631 (hexadecimal) which is
equivalent to 00000110 00110001 in binary.
Most of the commands that can be initiated using the write command are self
explanatory (Table 8.C). Two of these commands (Repeat Read and Cancel
Repeat Read) require an additional explanation:
REPEAT READ - The repeat read command instructs the decoder to wait for
data. When data becomes available, the decoder will then send the data to