Description Of Pin Functions; P00 To P07 (Port 0); P20, P21 (Port 2); P40 To P43 (Port 4) - NEC PD789860 User Manual

3.2 Description of Pin Functions

3.2.1 P00 to P07 (Port 0)

These pins constitute an 8-bit I/O port and can be set to input or output port mode in 1-bit units by using port mode
register 0 (PM0).

3.2.2 P20, P21 (Port 2)

These pins constitute a 2-bit I/O port. In addition, these pins function as the timer input/output and bit sequential
buffer output.
Port 2 can be set to the following operation modes in 1-bit units.
(1) Port mode
In port mode, P20 and P21 function as a 2-bit I/O port. Port 2 can be set to input or output port mode in 1-bit
units by using port mode register 2 (PM2).
(2) Control mode
In this mode, P20 and P21 function as the timer input/output and the bit sequential buffer output.
(a) BSFO
This is the output pin of the bit sequential buffer.
(b) TMI
This is the external clock input pin for the timer 40.
(c) TMO
This is the output pin of the timer 40.

3.2.3 P40 to P43 (Port 4)

These pins constitute a 4-bit input-only port. In addition, these pins function as the key return input.
(1) Port mode
In port mode, P40 to P43 function as a 4-bit input-only port. For mask ROM versions, an on-chip pull-up
resistor can be specified by means of the mask option.
(2) Control mode
In this mode, P40 to P43 function as the key return input (KR10 to KR13).

3.2.4 RESET

An active-low system reset signal is input to this pin.
µ
3.2.5 X1, X2 ( PD789860 Subseries)
These pins are used to connect a crystal resonator for system clock oscillation.
To supply an external clock, input the clock to X1 and input the inverted signal to X2.
µ
3.2.6 CL1, CL2 ( PD789861 Subseries)
These pins are used to connect a resistor (R) and capacitor (C) for system clock oscillation.
To supply an external clock, input the clock to CL1 and input the inverted signal to CL2.
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CHAPTER 3 PIN FUNCTIONS
User's Manual U14826EJ5V0UD