UPD78F0138 NEC, UPD78F0138 Datasheet - Page 103

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

4.2.4 Port 3
using port mode register 3 (PM3). When 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 3 (PU3).
Port 3 is a 4-bit I/O port with an output latch. Port 3 can be set to the input mode or output mode in 1-bit units
This port can also be used for external interrupt request input.
RESET input sets port 3 to input mode.
Figures 4-12 and 4-13 show block diagrams of port 3.
PU3:
PM3:
RD:
WR××: Write signal
WR
WR
WR
RD
PORT
PM
PU
Read signal
Pull-up resistor option register 3
Port mode register 3
PM30 to PM32
PU30 to PU32
(P30 to P32)
Output latch
Alternate
function
PM3
PU3
Figure 4-12. Block Diagram of P30 to P32
CHAPTER 4 PORT FUNCTIONS
User’s Manual U16228EJ2V0UD
EV
DD
P-ch
P30/INTP1 to
P32/INTP3
103