NEC uPD78P078 - Manual (Page 89)

89
CHAPTER 4 PIN FUNCTION (
µ
PD78078Y SUBSERIES)
4.2.3 P20 to P27 (Port 2)
These are 8-bit input/output ports. Besides serving as input/output ports, they function as data input/output to/
from the serial interface, clock input/output, automatic transmit/receive busy input, and strobe output functions.
The following operating modes can be specified bit-wise.
(1) Port mode
These ports function as 8-bit input/output ports. They can be specified bit-wise as input or output ports with
port mode register 2 (PM2). When they are used as input ports, on-chp pull-up resistors can be connected
to them by defining the pull-up resistor option register L (PUOL).
(2) Control mode
These ports function as serial interface data input/output, clock input/output, automatic transmit/receive busy
input, and strobe output functions.
(a) SI0, SI1, SO0, SO1, SB0, SB1, SDA0, SDA1
Serial interface serial data input/output pins
(b) SCK0, SCK1, SCL
Serial interface serial clock input/output pins
(c) BUSY
Serial interface automatic transmit/receive busy input pins
(d) STB
Serial interface automatic transmit/receive strobe output pins
Caution When this port is used as a serial interface, the I/O and output latches must be set
according to the function the user requires. For the setting, refer to Figure 18-4. Serial
Operation Mode Register 0 Format and Figure 19-3. Serial Operation Mode Register 1
Format.