Rockwell Automation 1734-485ASC POINT I/O ASCII User Manual - Manual (Page 42)

Publication 1734-UM009B-EN-P - July 2003
2-16 Configuring Your ASCII Module
Setting Up and Using Pad Mode
Pad Mode operation adds extra characters to the end of its received
data string (after the delimiter character). These characters are added
from the external I/O device before sending the string to the
DeviceNet scanner (master) as an I/O response.
The quantity added is such that the data string returned to the scanner
is always a constant length, and that length is the number specified in
the maximum Receive Character Length parameter plus the 4-byte
header. The quantity of pad characters sent can vary from message to
message, depending upon the size of the incoming string.
Pad Mode Selection
Pad Mode allows for compatibility with scanners that cannot receive
variable length I/O messages. For such scanners, you must turn Pad
mode ON (a value of 1). Turning Pad mode ON will not harm Scan-
ners that do support variable length receive messages.
The default value for Pad Mode is ON. If your scanner does support
variable I/O messaging lengths, you may turn OFF the Pad Mode
option (a value of 0) to conserve some network bandwidth.
The selection of Pad Mode is valid only for the DeviceNet message
that the ASCII module produces. It has no effect on DeviceNet
messages sent from the scanner to the ASCII module. This value can
be set and retrieved by using the standard set and get services on class
15 (F
hex
), instance 9, attribute 1.
Pad Mode Character
The ASCII modules allow you to specify the character that Pad Mode
uses to pad the received serial data. This can be set to any valid I/O
value (0-127 in 7 bit modes, 0-255 in 8 bit modes). This value can be
set and retrieved by using the standard set and get services on class 15
(F
hex
), instance 10, attribute 1.