Rockwell Automation 1734-485ASC POINT I/O ASCII User Manual - Manual (Page 21)

Publication 1734-UM009B-EN-P - July 2003
Installing the ASCII Module 1-11
Setting Up DeviceNet
Communications The ASCII module supports 4 modes of data transfer of the serial
buffer:
· Polled I/O
· Change of State I/O
· Cyclic I/O
· Explicit Message
Polled I/O
The ASCII module monitors the transaction ID for a change in the
transaction ID. If the transaction ID changes, then the ASCII module
transmits the data buffer on its serial link. If the transaction ID does
not change, then the device does not transmit the data buffer.
After the device has transmitted its data out to the serial link, the ASCII
module then takes any information that is stored in its current serial
input buffer and sends this data to the DeviceNet master. It sends all
characters up to and including the received delimiter, including pad
characters if not deselected.
When the ASCII module receives a new message (either with a
delimiter or with an overflow condition without a delimiter) the
device then increments the receive record, updates the length byte,
and copies the new information from the last receive delimiter into
the buffer. If an overflow occurs, the ASCII module indicates so in its
receive status bit. The receive status byte also reflects parity errors in
the device.