GMS81C2020 Datasheet, PDF(43/92 Page) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

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GMS81C2020 Datasheet, PDF (43/92 Pages) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

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Hyundai Micro Electronics

GMS81C2020/GMS81C2120

12. I/O PORTS

The GMS81C2020 has eight ports, R0, R1, R2, R3, R4,

R5, R6 and R7. The GMS81C2120 has five ports, R0,

R2, R3, R5 and R6. These ports pins may be multiplexed

with an alternate function for the peripheral features on the

device. 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 R0 as output

ports and the odd numbered bits as input ports, write "55H"

to address C1H (R0 direction register) during initial setting

as shown in Figure 12-1 .

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

R0 DATA

R0 DIRECTION

R1 DATA

R1 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 12-1 Example of port I/O assignment

12.1 RA(Vdisp) register

RA is one-bit high-voltage input only port pin. In addition,

RA serves the functions of the Vdisp special features. Vdisp

is used as a high-voltage input power supply pin when se-

lected by the mask option..

RA Data Register

ADDRESS : FBH

RESET VALUE : Undefined

- - - - - - - RA0

INPUT DATA

Port pin

Alternate function

Vdisp (High-voltage input power supply)

12.2 R0 and R0IO registers

R0 is an 8-bit high-voltage CMOS bidirectional I/O port

(address C0H). Each port can be set individually as input

and output through the R0IO register (address C1H). Each

port can directly drive a vacuum fluorescent display. R03

port is multiplexed with Buzzer Output Port(BUZO), R02

port is multiplexed with Event Counter Input Port (EC0),

and R01~R00 are multiplexed with External Interrupt In-

put Port(INT1, INT0).

R0 Data Register

ADDRESS : C0H

RESET VALUE : Undefined

R07 R06 R05 R04 R03 R02 R01 R00

R0 Direction Register

R0IO

INPUT / OUTPUT DATA

ADDRESS : C1H

RESET VALUE : 00000000

DIRECTION SELECT

0 : INPUT PORT

1 : OUTPUT PORT

R0 Function Selection Register

R0FUNC

ADDRESS : F4H

RESET VALUE : ----0000

BUZO EC0 INT1 INT0

0 : R03

1 : BUZO

0 : R02

1 : EC0

0 : R00

1 : INT0

0 : R01

1 : INT1

Figure 12-2 Registers of Port R0

The control register R0FUNC (address F4H) controls to se-

lect alternate function. After reset, this value is "0", port

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

tion such as Buzzer Output, External Event Counter Input

and External Interrupt Input, write "1" to the correspond-

ing bit of R0FUNC. Regardless of the direction register

R0IO, R0FUNC is selected to use as alternate functions,

port pin can be used as a corresponding alternate features

(BUZO, EC0, INT1, INT0)

PORT

R03/

BUZO

R02/

EC0

R01/

INT1

R0FUNC

[3:0]

Description

R00 (Normal I/O Port)

BUZO (Buzzer Output Port)

R01 (Normal I/O Port)

EC0 (Event Counter Input Port)

R01 (Normal I/O Port)

INT1 (External interrupt 1 Input

Port)

Nov. 1999 Ver 0.0

preliminary

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