Publication 1734-UM009A-EN-P - June 2002
1-10 Installing the RS-232 ASCII Module
Setting Up DeviceNet
Communications
The 1734-232ASC 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 1734-232ASC module monitors the transaction ID for a change in
the transaction ID. If the transaction ID changes, then the
1734-232ASC 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
1734-232ASC 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 1734-232ASC 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 1734-232ASC module indicates
so in its receive status bit. The receive status byte also reflects parity
errors in the device.
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