Data Sheet

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Mates with:#19, #20
Details
This is a "full" serial port that can be electronically programmed to work in RS232, RS422, or RS485
mode. The Tibbit is based on the Sipex SP337 universal transceiver.
Mode selection is through FD/HD and 232/422-485 control lines:
Mode FD/-HD -232/422-485
RS232 HIGH LOW
RS422 HIGH HIGH
RS485 LOW HIGH
When unconnected, FD/-HD defaults to HIGH, while -232/422-485 defaults to LOW. This means that
the RS232 mode will be selected.
In the RS232 mode the port has RX, TX, RTS, CTS, DTR, and DSR signals. This is the full-duplex mode.
In the RS422 mode the port has +/-RX, +/-TX, +/-RTS, and +/-CTS signal pairs. This is the full-duplex
mode.
In the RS485 mode the port has only +/-RX and +/-TX signal pairs. This is the half-duplex mode, so
you can connect +RX to +TX, and -RX to -TX. This will allow your system to communicate over a
single twisted pair. Direction control is through the RTS line — the line shall be LOW for data input
and HIGH for output.
For "normal" RS232/422/485 applications, this Tibbit has to be connected to the TX and RX lines of
the CPU's UART (see [SER] ). Planning to use RTS/CTS ow control as well? An interrupt line must be
available, too (see [INT] ).
Combining this Tibbit with the "C" device #19 (DB9M connector) will create a serial port with the
following pin assignment on the DB9M: