Datasheet

CHAPTER 4 PORT FUNCTIONS
User’s Manual U18698EJ1V0UD
79
4.2.1 Port 1
Port 1 is a 2-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 P12 and P13 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 key interrupt input and serial interface data I/O.
Reset signal generation sets port 1 to input mode.
Figures 4-2 and 4-3 show block diagrams of port 1.
Figure 4-2. Block Diagram of P12
WR PU
RD
PU1
PM1
WR
PORT
WR PM
V DD
P-ch
P1
PU12
PM12
P12/RxD0/KR3/<RxD6>
Output latch
(P12)
Internal bus
Selector
Alternate
function
P1: Port register 1
PU1: Pull-up resistor option register 1
PM1: Port mode register 1
RD: Read signal
WR××: Write signal