Rockwell Automation 1734-485ASC POINT I/O ASCII User Manual - Manual (Page 51)

Publication 1734-UM009B-EN-P - July 2003
Configuring Your ASCII Module 2-25
A transmission of the serial data from the ASCII module to your ASCII
device can be initiated in two ways. If an I/O connection is used,
serial data in the mapped I/O location will be sent to the ASCII
module on every I/O command (repeatedly at the same interval of the
DeviceNet scanner).
· In Transmit Handshake Mode, changing the transaction ID will
always initiate a transmission on the network. Even if you do not
set new data into the data string, the old data will be
transmitted.
· In Transmit Immediate Mode, the ASCII module will transmit
data out its serial port every time it receives an I/O command or
explicit message to its transmit buffer or changes the transaction
ID.
ATTENTION
!
An I/O message is repeatedly sent and generates
internal writes to Class 71, Instance 1, attribute 3.
This will cause you to send large amounts of data to
your device and can cause TX Buffer Overflows. You
may experience corrupted data and improper
information sent to your serial device when using
data only mode with I/O messaging.
ATTENTION
!
You should take care when activating Transmit
Immediate mode while I/O Polling is active. In this
mode of operation, the module will continuously
transmit serial data to the target serial device. If the
data string represents a command message to your
target device, these actions could result in
unintended misoperationg of your device or system.