Port 1 - NEC 78K0 User Manual

4.2.2 Port 1

Port 1 is an 8-bit I/O port with an output latch. Port 1 can be set to the input mode or output mode in 1-bit units
using port mode register 1 (PM1). When the P10 to P17 pins are used as an input port, use of an on-chip pull-up
resistor can be specified by pull-up resistor option register 1 (PU1).
This port can also be used for external interrupt request input, serial interface data I/O, clock I/O, and timer I/O.
RESET input sets port 1 to input mode.
Figures 4-4 to 4-8 show block diagrams of port 1.
Caution When P10/SCK10/TxD0, P11/SI10/RxD0, and P12/SO10 are used as general-purpose ports, do not
write to serial clock selection register 10 (CSIC10).
WR
PU
RD
WR
PORT
Output latch
WR
PM
PU1: Pull-up resistor option register 1
PM1: Port mode register 1
RD: Read signal
WR××: Write signal
80
CHAPTER 4 PORT FUNCTIONS
Figure 4-4. Block Diagram of P10
PU1
PU10
Alternate
function
(P10)
PM1
PM10
Alternate
function
User's Manual U16227EJ2V0UD
EV
DD
P-ch
P10/SCK10/TxD0