Specifications

I-32 EPSON S1C6S2N7 TECHNICAL HARDWARE

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (I/O Ports)

Input or output mode can be set for the four bits of I/O port

P00–P03 by writing data into I/O control register IOC.

To set the input mode, 0 is written to the I/O control regis-

ter. When an I/O port is set to input mode, its impedance

becomes high and it works as an input port. However, the

input line is pulled down when input data is read.

The output mode is set when 1 is written to the I/O control

as an output port, it outputs a high signal (VDD) when the

port output data is 1, and a low signal (VSS) when the port

output data is 0.

After an initial reset, the I/O control register is set to 0, and

the I/O port enters the input mode.

The output specification during output mode (IOC = 1) of the

I/O port can be set with the mask option for either comple-

mentary output or Pch open drain output. This setting can

be performed for each bit of the I/O port. However, when

Pch open drain output has been selected, voltage in excess

of the supply voltage must not be applied to the port.

Mask option

I/O control register

and I/O mode

Table 4.5.1 lists the I/O port control bits and their ad-

dresses.

Control of I/O port

Table 4.5.1 I/O port control bits

Address Comment

D3 D2 D1 D0 Name SR 1 0

0F6H

P03 P02 P01 P00 P03

P02

P01

P00

–

I/O port (P00–P03)

High

Low

R/W

0FCH

00 0IOC

IOC

I/O port P00–P03 Input/Output

Output Input

R/W