Rockwell Automation 1734-485ASC POINT I/O ASCII User Manual - Manual (Page 43)

Publication 1734-UM009B-EN-P - July 2003
Configuring Your ASCII Module 2-17
Setting Up and Using the Swap Bytes Mode
This option may be helpful if the ASCII module is connected to a
DeviceNet scanner that organizes the data string characters into data
type elements that are larger than 1 byte each (i.e. SLC500). In such
cases, the bytes of the data in the master’s memory organization can
be reversed from the order in which they are sent or received on the
DeviceNet and the serial link to the ASCII device. This may cause
errors in some cases. Thus, the received string “ABCDEFGH” may
appear in memory as “BADCFEHG” for 2-byte word organization, and
“DCBAHGFE” for 4-byte word organization.
Transmit Byte Swapping
By setting Parameter 21 (class F
hex
, instance 21, attribute 1), the bytes
from the master will be swapped by the ASCII module before
transmitting the string to the ASCII device.
Receive Byte Swapping
By setting Parameter 11 (class F
hex
, instance 11, attribute 1), the ASCII
module will re-order the bytes received from your ASCII device before
sending the string to the master.
Maximum Number of Receive Characters Parameter Rules for Usage
· Swap Bytes Mode is set for transmit and receive independently.
· The byte swapping works best if the max RX and TX lengths are
multiples of the byte-swap size.