GMS87C2020 datasheet(67/92 Pages) HYNIX

67 / 92 page

Hyundai Micro Electronics

GMS81C2020/GMS81C2120

Nov. 1999 Ver 0.0

preliminary

The interrupts are controlled by the interrupt master enable

flag I-flag (bit 2 of PSW), the interrupt enable register

(IENH, IENL) and the interrupt request flags (in IRQH,

IRQL) except Power-on reset and software BRK interrupt.

Interrupt enable registers are shown in Figure 19-2 . These

registers are composed of interrupt enable flags of each in-

terrupt source, these flags determines whether an interrupt

will be accepted or not. When enable flag is "0", a corre-

sponding interrupt source is prohibited. Note that PSW

contains also a master enable bit, I-flag, which disables all

interrupts at once.

Figure 19-2 Interrupt Enable Registers and Interrupt Request Registers

When an interrupt is occured, the I-flag is cleared and dis-

able any further interrupt, the return address and PSW are

pushed into the stack and the PC is vectored to. Once in the

interrupt service routine the source(s) of the interrupt can

be determined by polling the interrupt request flag bits.

The interrupt request flag bit(s) must be cleared by soft-

ware before re-enabling interrupts to avoid recursive inter-

rupts. The Interrupt Request flags are able to be read and

written.

Reset/Interrupt

Symbol

Priority

Vector Addr.

Hardware Reset

External Interrupt 0

External Interrupt 1

Timer 0

Timer 1

A/D Converter

Watch Dog Timer

Basic Interval Timer

Serial Interface

RESET

INT0

INT1

Timer 0

Timer 1

A/D C

WDT

BIT

SPI

FFFEH

FFFAH

FFF8H

FFF6H

FFF4H

FFF2H

FFF0H

FFEEH

FFECH

FFEAH

FFE8H

FFE6H

Table 19-1 Interrupt Priority

IENH

ADDRESS : E2H

RESET VALUE : 0000----

INT0E

INT1E

T0E

T1E

Interrupt Enable Register High

IENL

ADDRESS : E3H

RESET VALUE : 0000----

ADE

WDTE

BITE

SPIE

Interrupt Enable Register Low

IRQH

ADDRESS : E4H

RESET VALUE : 0000----

INT0IF

INT1IF

T0IF

T1IF

Interrupt Request Register High

IRQL

ADDRESS : E5H

RESET VALUE : 0000----

ADIF

WDTIF

BITIF

SPIIF

Interrupt Request Register Low

0 : Disable

1 : Enable

Enables or disables the interrupt individually

If flag is cleared, the interrupt is disabled.

0 : Not occurred

1 : Interrupt request is occurred

Shows the interrupt occurrence

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