NEC 78K0 Series User Manual page 108

5.2.2 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 in 1-bit units 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 signal generation sets port 1 to input mode.
Figures 5-8 to 5-12 show block diagrams of port 1.
Caution To use P10/SCK10/TxD0 and P12/SO10 as general-purpose ports, set serial operation mode
register 10 (CSIM10) and serial clock selection register 10 (CSIC10) to the default status (00H).
WR
PU
RD
WR
PORT
Output latch
WR
PM
P1: Port register 1
PU1: Pull-up resistor option register 1
PM1: Port mode register 1
RD: Read signal
WR××: Write signal
108
CHAPTER 5 PORT FUNCTIONS
Figure 5-8. Block Diagram of P10
PU1
PU10
Alternate
function
P1
(P10)
PM1
PM10
Alternate
function
Preliminary User's Manual U17260EJ3V1UD
EV
DD
P-ch
P10/SCK10/TxD0