Port 0 - NEC 78K0/KB1+ Preliminary User's Manual

4.2.1 Port 0

Port 0 is a 4-bit I/O port with an output latch. Port 0 can be set to the input mode or output mode in 1-bit units
using port mode register 0 (PM0). When the P00 to P03 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 0 (PU0).
This port can also be used for timer I/O.
RESET input sets port 0 to input mode.
Figures 4-2 to 4-4 show block diagrams of port 0.
WR
PU
RD
WR
PORT
WR
PM
PU0: Pull-up resistor option register 0
PM0: Port mode register 0
RD: Read signal
WR××: Write signal
66
CHAPTER 4 PORT FUNCTIONS
Figure 4-2. Block Diagram of P00
PU0
PU00
Alternate function
Output latch
(P00)
PM0
PM00
Preliminary User's Manual U16846EJ1V0UD
V
DD
P-ch
P00/TI000