Serial Interface Circuit - Citizen CBM-202PC-04 User Manual

4.13 Serial Interface Circuit

A serial interface is an asynchronous serial system. When the serial interface is not used, pull
up RXD (Pin 15) and DSR (Pin 100) of the CPU with a 47k resistor.
1) Circuit
2) Signal names and their functions
Signal Name
TXD
RXD
DSR
DTR
Pin No. Input/Output
13 Output
15 Input
100 Input
12 Output
Transmits the status.
If data reception is disabled when XON/XOFF
is selected, XOFF(13H) will be transmitted,
and if data reception is enabled, XON(11H)
will be transmitted.
Received data signal.
parity error occurs, the relevant data will be
printed "?".
With DTR/DSR selected, if this signal is
"LOW," the data will be transmitted from the
CPU. If "HIGH,"
transmitted after the signal is turned to
"LOW."
Transmit the data when this signal is "LOW."
If written when it is "HIGH," an overrun error
will result, ignoring the data.
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CBM-202PC-04 User's Manual
Function
If a framing error or
the data will be
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