UPD17708 datasheet(114/356 Pages) NEC

114 / 356 page

µPD17704, 17705, 17707, 17708, 17709

114

11.3.2 Using input port

The input data is read by executing a read instruction (such as SKT) to the port register corresponding to

the port pin.

“1” is read from the port register when a high level is input to the corresponding port pin; when a low level

is input to the port pin, “0” is read from the register.

Nothing is affected even if a write instruction (such as MOV) is executed to the port register.

P0D has a pull-down resistor that can be connected or disconnected by software in 1-bit units. The pull-down

resistor is connected when “0” is written to the corresponding bit of the port 0D pull-down resistor selection

11.3.3 Port 0D pull-down resistor selection register

The port 0D pull-down resistor selection register specifies whether a pull-down resistor is connected to P0D3

through P0D0 pins. The configuration and function of this register are illustrated below.

•

Port 0D pull-down resistor selection register

Name

Flag symbol

Address

(BANK15)

66H

Read/Write

R/W

Port 0D pull-down resistor

selection

Power-ON reset

WDT&SP reset

CE reset

Clock stop

Connects pull-down resistor to P0D0 pin

Disconnects pull-down resistor from P0D0 pin

Selects pull-down resistor of P0D0 pin

Retained

Connects pull-down resistor to P0D1 pin

Disconnects pull-down resistor from P0D1 pin

Selects pull-down resistor of P0D1 pin

Connects pull-down resistor to P0D2 pin

Disconnects pull-down resistor from P0D2 pin

Selects pull-down resistor of P0D2 pin

Connects pull-down resistor to P0D3 pin

Disconnects pull-down resistor from P0D3 pin

Selects pull-down resistor of P0D3 pin

UPD17708 Datasheet(PDF) 114 Page - NEC