HD6433308 Datasheet, PDF (108/349 Pages) Hitachi Semiconductor – Hitachi Single-Chip MicroComputer

used for serial communication.
MOS Pull-Ups: Are available for input pins, including serial communication input pins. Software
can turn the MOS pull-up on by writing a “1” in P5DR, and turn it off by writing a “0.”
Pin P50: This pin can be used for general-purpose input or output, or for output of asynchronous
serial transmit data (ATxD). When used for ATxD output, this pin is unaffected by the values in
P5DDR and P5DR, and its MOS pull-up is automatically turned off.
Pin P51: This pin can be used for general-purpose input or output, or for input of asynchronous
serial receive data (ARxD). When used for ARxD input, this pin is unaffected by P5DDR and
P5DR, except that software can turn on its MOS pull-up by clearing its data direction bit to "0" and
setting its data bit to "1."
Pin P52: This pin can be used for general-purpose input or output, or for asynchronous serial clock
input or output (ASCK). When used for ASCK input or output, this pin is unaffected by P5DDR
and P5DR, except that software can turn on its MOS pull-up by clearing its data direction bit to "0"
and setting its data bit to "1." For ASCK usage, the MOS pull-up should be turned off.
Reset and Hardware Standby Mode: A reset or entry to the hardware standby mode makes all
pins of port 5 into input port pins with the MOS pull-ups off.
Software Standby Mode: In the software standby mode, the serial control register is initialized
but P5DDR and P5DR remain in their previous states. All pins become input or output port pins
depending on the setting of P5DDR. Output pins output the values in P5DR. The MOS pull-ups of
input pins are on or off depending on the values in P5DR.
Figures 5-6 to 5-8 show schematic diagrams of port 5.
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