User`s manual

CBM-202PC-04 User’s Manual
23 CITIZEN
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 Pin No. Input/Output Function
TXD 13 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.
RXD 15 Input
Received data signal. If a framing error or
parity error occurs, the relevant data will be
printed "?".
DSR 100 Input
With DTR/DSR selected, if this signal is
"LOW," the data will be transmitted from the
CPU. If "HIGH," the data will be
transmitted after the signal is turned to
"LOW."
DTR 12 Output
Transmit the data when this signal is "LOW."
If written when it is "HIGH," an overrun error
will result, ignoring the data.