Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 120)

Chapter 8
Host Commands Using the RS-485 Interface
8–8
Continue read commands until a 00 (hexadecimal) status code is received
indicating completion of the read. After the last segment of the data packet
is sent, the data packet is removed from the decoder’s host port buffer.
TRANSACTION WORD (Bytes 2 &3) - The transaction word (2 bytes) is
the same as the transaction word sent with the Read Command.
DATA (Bytes 4 through 123)- Following the transaction word is the data (up
to 124 bytes).
Unprotected Read Example
To help you understand how to use the unprotected read command, we have
provided the following example. In this example we are going to read the
contents of output counter #1 (contains count of 9).
UNPROTECTED READ
00000001
Read Command
HI Byte LOW Byte
10101010 10101010
Transaction Word
00000110 00000100
Counter Address
00000000 00000010
2 Bytes Returned
00000000
Status
UNPROTECTED READ REPLY
HI Byte LOW Byte
10101010 10101010
Transaction Word
00000000 00001001
Count of 9
01000001
Read Reply
00000000
Status-Successful