UPD64 datasheet(16/68 Pages) NEC

16 / 68 page

µPD63, 63A, 64

3.2 KI Port/Special Ports (P1)

3.2.1 KI port (P11: bits 4-7 of P1)

The KI port is to the 4-bit input port for key entry.

The pin state can be read.

Software can be used to set the availability of the pull-down resistor of the KI port in 4-bit units by means of bit

5 of the P4 register.

When reset, the pull-down resistor is connected.

Table 3-3. KI/Special Port Register (P1)

Bit

Name

KI3

KI2

KI1

KI0

S1/LED

(Fixed to “1”)

: In INPUT mode, state of the S0 pin is read (Read only).

In OFF mode, this bit is fixed to “1”.

: The state of the S1/LED pin is read regardless of INPUT/OUTPUT mode (Read only).

b4-b7

: The state of the KI pin is read (Read only).

Caution In order to prevent malfunction, be sure to input a low level to more than one of pins KI0 to KI3

when reset is released (when RESET pin changes from low level to high level, or POC is released

due to supply voltage startup).

3.2.2 S0 port (P1’s bit 2)

The S0 port is the INPUT/OFF mode port.

The pin state can be read by setting this port to INPUT mode with bit 0 of the P4 register.

In INPUT mode, software can be used to set the availability of the pull-down resistor of the S0 and S1/LED port

in 2-bit units by means of bit 4 of the P4 register.

If INPUT mode is canceled (thus set to OFF mode), the pin becomes high-impedance but it also makes that the

through current does not flow internally. In OFF mode, “1” can be read regardless of the pin state.

When reset, it is set to OFF mode, thus becoming high-impedance.

3.2.3 S1/LED (port bit 3 of P1)

The S1/LED port is the input/output port.

It uses bit 2 of the P4 register to set INPUT or OUTPUT mode. The pin state can be read in both INPUT mode

and OUTPUT mode.

When in INPUT mode, software can be used to set the availability of the pull-down resistor of the S0 and

S1/LED ports in 2-bit units by means of bit 4 of the P4 register.

When in OUTPUT mode, the pull-down resistor is automatically disconnected thus becoming the remote control

transmission display pin (refer to 4. TIMER).

When reset, it is placed in OUTPUT mode, and high level is output.

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