GMS87C1404 데이터 시트보기 (PDF) - Hyundai Micro Electronics

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GMS87C1404

CMOS SINGLE-CHIP 8-BIT MICROCONTROLLER

Hyundai Micro Electronics 

HYUNDAI MicroElectronics

GMS87C1404/GMS87C1408

9. I/O PORTS

The GMS87C1408 and GMS87C1404 has four ports, RA,

RB, RC and RD. These ports pins may be multiplexed with

an alternate function for the peripheral features on the de-

vice. In general, when a initial reset state, all ports are used

as a general purpose input port.

All pins have data direction registers which can set these

ports as output or input. A “1” in the port direction register

defines the corresponding port pin as output. Conversely,

write “0” to the corresponding bit to specify as an input

pin. For example, to use the even numbered bit of RA as

output ports and the odd numbered bits as input ports, write

“55H” to address C1H (RA direction register) during initial

setting as shown in Figure 9-1 .

9.1 RA and RAIO registers

RA is an 8-bit bidirectional I/O port (address C0H). Each

port can be set individually as input and output through the

RAIO register (address C1H).

RA7~RA1 ports are multiplexed with Analog Input Port

(AN7~AN1) and RA0 port is multiplexed with Event

Counter Input Port (EC0).

RA Data Register

ADDRESS : C0H

RESET VALUE : Undefined

RA

RA7 RA6 RA5 RA4 RA3 RA2 RA1 RA0

RA Direction Register

RAIO

INPUT / OUTPUT DATA

ADDRESS : C1H

RESET VALUE : 00000000

DIRECTION SELECT

0 : INPUT PORT

1 : OUTPUT PORT

RA Function Selection Register

RAFUNC

ADDRESS : CAH

RESET VALUE : 00000000

ANSEL7 ANSEL6 ANSEL5 ANSEL4 ANSEL3 ANSEL2 ANSEL1 ANSEL0

0 : RA4

1 : AN4

0 : RA5

1 : AN5

0 : RA6

1 : AN6

0 : RA7

1 : AN7

0 : RB0

1 : AN0

0 : RA1

1 : AN1

0 : RA2

1 : AN2

0 : RA3

1 : AN3

Figure 9-2 Registers of Port RA

The control register RAFUNC (address CAH) controls to

Reading data register reads the status of the pins whereas

writing to it will write to the port latch.

WRITE “55H” TO PORT RA DIRECTION REGISTER

C0H

C1H

C2H

C3H

RA DATA

RA DIRECTION

RB DATA

RB DIRECTION

01010101

7 6 5 4 3 2 1 0 BIT

IOIOIOIO

7 6 5 4 3 2 1 0 PORT

I: INPUT PORT

O: OUTPUT PORT

Figure 9-1 Example of port I/O assignment

select alternate function. After reset, this value is “0”, port

may be used as general I/O ports. To select alternate func-

tion such as Analog Input or External Event Counter Input,

write “1” to the corresponding bit of RAFUNC.Regardless

of the direction register RAIO, RAFUNC is selected to use

as alternate functions, port pin can be used as a correspond-

ing alternate features (RA0/EC0 is controlled by RB-

FUNC)

PORT

RAFUNC.7~0

Description

RA7/AN7

0

RA7 (Normal I/O Port)

1

AN7 (ADS2~0=111)

RA6/AN6

0

RA6 (Normal I/O Port)

1

AN6 (ADS2~0=110)

RA5/AN5

0

RA5 (Normal I/O Port)

1

AN5 (ADS2~0=101)

RA4/AN4

0

RA4 (Normal I/O Port)

1

AN4 (ADS2~0=100)

RA3/AN3

0

RA3 (Normal I/O Port)

1

AN3 (ADS2~0=011)

RA2/AN2

0

RA2 (Normal I/O Port)

1

AN2 (ADS2~0=010)

RA1/AN1

0

RA1 (Normal I/O Port)

1

AN1 (ADS2~0=001)

RA0/EC01

RA0 (Normal I/O Port)

EC0 (T0CK2~0=111)

1. This port is not an Analog Input port, but Event Counter clock

source input port. ECO is controlled by setting TOCK2~0 =

111. The bit RAFUNC.0 (ANSEL0) controls the RB0/AN0/AVref

port (Refer to Port RB).

Oct. 1999 Ver 1.0

29

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