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LT 1804 Product Reference Guide: Programming the LT 1804
Communication Protocols
Hardware Handshaking
The data interface consists of an RS-232C port. See
page
3-7. The port has been designed to operate either with or without
hardware handshaking lines, RTS, Request to Send, and CTS, Clear to Send.
If RTS/CTS handshaking has not been selected, scan data is transmitted as it
becomes available. If optional RTS/CTS handshaking has been selected, the
DTR signal is hardwired active, and the unit proceeds as follows:
Examine CTS. If CTS is not asserted by the host, RTS is asserted by the
•
scanner. If CTS is asserted by the host, the scanner waits up to 2 seconds
for CTS to be negated.
When the host asserts CTS in response to and within the programmable
•
response timeout period of the scanner's RTS, data is transmitted.
The scanner negates RTS after sending the last character.
•
The host should respond by negating CTS. The scanner does not wait for
•
this but checks before the next transmission, as above.
If the above communication attempt fails, the scanner issues an error beep
•
to alert the operator that the data was not successfully transmitted. In this
case, the data is lost and must be rescanned.
See
Handshaking Sequence on page
4-23.
4-21
Interface Cable Pinouts on
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