GMS81C2012 datasheet(39/107 Pages) HYNIX

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HYUNDAI MicroElectronics

GMS81C2012/GMS81C2020

MAR. 2000 Ver 1.00

9. I/O PORTS

The GMS81C20xx has eight ports (R0, R1, R2, R4, R5, R6

and R7).These ports pins may be multiplexed with an alter-

nate function for the peripheral features on the device.

All pins have data direction registers which can define

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

Conversely, write “0” to the corresponding bit to specify it

as 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 0C1H (R0 port direction reg-

ister) during initial setting as shown in Figure 9-1.

All the port direction registers in the GMS81C2020 have 0

written to them by reset function. On the other hand, its in-

itial status is input.

Figure 9-1 Example of Port I/O Assignment

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 selected by the mask option.

R0 and R0IO register: R0 is an 8-bit high-voltage CMOS

bidirectional I/O port (address 0C0H). Each port can be set

individually as input and output through the R0IO register

(address 0C1H). Each port can directly drive a vacuum flu-

orescent display. R03 port is multiplexed with Buzzer Out-

put Port(BUZO),

R02 port is multiplexed with Event

Counter Input Port (EC0), and R01~R00 are multiplexed

with External Interrupt Input Port(INT1, INT0)

.The control register R0FUNC (address F4H) controls to

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 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 pin

Alternate function

Vdisp (High-voltage input power supply)

I : INPUT PORT

WRITE "55H" TO PORT R0 DIRECTION REGISTER

0 1 0 1 0 1 0 1

I O I O I O I O

R0 data

R1 data

R0 direction

R1 direction

0C0H

0C1H

0C2H

0C3H

7 65432 10

BIT

7654 3210

PORT

O : OUTPUT PORT

RA Data Register

ADDRESS: 0FBH

RESET VALUE: Undefined

RA0

Input data

Port Pin

Alternate Function

R00

R01

R02

R03

INT0 (External interrupt 0 Input Port)

INT1 (External interrupt 1 Input Port)

EC0 (Event Counter Input Port)

BUZO (Buzzer Output Port)

R0 Data Register

ADDRESS: 0C0H

RESET VALUE: Undefined

R07 R06 R05 R04 R03 R02 R01 R00

Port Direction

R0 Direction Register

R0IO

ADDRESS : 0C1H

RESET VALUE : 00H

0: Input

1: Output

Input / Output data

R0 Function Selection Register

R0FUNC

ADDRESS : 0F4H

RESET VALUE : ----0000B

0: R00

1: INT0

0: R01

1: INT1

0: R02

1: BUZO

0: R03

1: EC0

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