UPD78044F datasheet(87/472 Pages) NEC

87 / 472 page

Chapter 4

Port Functions

User’s Manual U16504EE1V1UD00

4.2.1 Port 0

Port 0 is an 4-bit input/output port with output latch. P00 to P03 pins can specify the input mode/output

mode in 1-bit units with the port mode register 0 (PM0). When P00 to P03 pins are used as input pins,

a pull-up resistor can be connected to them bit-wise with the pull-up resistor option register (PUm).

Dual-function includes external interrupt request input and the external clock input for the DCAN

peripheral.

RESET input sets port 0 to input mode.

Figure 4-2 shows block diagram of port 0.

Caution:

Because port 0 also serves for external interrupt request input, when the port func-

tion output mode is specified and the output level is changed, the interrupt request

flag is set. Thus, when the output mode is used, set the interrupt mask flag to 1, in

order to avoid an factorized interrupt.

Figure 4-2:

P00 to P03 Configurations

Remarks: 1. PU0

: Pull-up resistor option register

2. PM

: Port mode register

3. RD

: Port 0 read signal

4. WR

: Port 0 write signal

P-ch

WRPM

WRPORT

WRPUO

VDD

P00/INTP0,

P01/INTP1,

P02/INTP2,

P03/CCLK

Selector

PU0

Output Latch

(P00 to P03)

PM00 to PM03

UPD78044F Datasheet(PDF) 87 Page - NEC