Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 124)

Chapter 8
Host Commands Using the RS-485 Interface
8–12
the host using a write command to a specific address in the host’s memory.
The host device does not have to request data, the decoder will automatically
send data as it is decoded.
The repeat read command has the following structure:
REPEAT READ COMMAND
00000000 00001000
TRANSACTION WORD
HI Byte LOW Byte
00000110 01000000
STARTING ADDRESS
REPEAT (r) SIZE (n)
HIGH AND LOW ADDRESS (Bytes 4 & 5) - Specifies the address for the
repeat read command (640 hexadecimal).
STARTING ADDRESS (Bytes 6 & 7) - The address of the host’s memory
where the first packet of data will be sent.
SIZE (n) (Byte 8) - The size specifies the the maximum number of bytes in
each message sent to the host and functions like a read reply.
REPEAT (r) (Byte 9) - This value determines the total number of data
packets or messages that can be sent to the host. If 0 is entered, then an
unlimited number of messages may be sent to the host.
After a Repeat Read command is sent to the decoder, the decoder will return
a write reply and then perform the repeat read function. The decoder will
continue to send data until the repeat count is reached, a Repeat Cancel
command is sent, or another Repeat Read command is received.
Writing to Configuration Area of Memory
Appendix D provides the address locations of the decoder’s configuration
memory. The host device can change the configuration of the decoder by
directly writing data into these memory locations. Refer to Chapter 4 for a