All of the bits that generate interrupts can be set or cleared by software, and it has the same

impact as done through hardware. In other words, interrupts or pending interrupts can be

generated or canceled in software.

The following content describes several SFR related to interrupt mechanism.

SFR: IE (Interrupt Enabling):

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

Bit-1

Bit-0

EA

ET2

ES

ET1

EX1

ET0

EX0

EA:

Global disables all interrupts when cleared.

ET2:

When set, enables Timer2 interrupt.

ES:

When set, enables the serial port interrupt.

ET1:

When set, enables Timer1 interrupt.

EX1:

When set, enables external interrupt 1.

ET0:

When set, enables Timer 0 interrupt.

EX0:

When set, enables external interrupt 0.

SFR: IP (Interrupt Priority Low):

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

Bit-1

Bit-0

-

-

PT2

PS

PT1

PX1

PT0

PX0

PT2:

If set, Set priority for timer2 interrupt higher

PS:

If set, Set priority for serial port interrupt higher

PT1:

If set, Set priority for timer1 interrupt higher

PX1:

If set, Set priority for external interrupt 1 higher

PT0:

If set, Set priority for timer0 interrupt higher

PX0:

If set, Set priority for external interrupt 0 higher

SFR: IPH (Interrupt Priority High):

Bit-7

Bit-6

Bit-5

Bit-4

Bit-3

Bit-2

Bit-1

Bit-0

PX3H

PX2H

PT2H

PSH

PT1H

PX1H

PT0H

PX0H

PX3H:

If set, Set priority for external interrupt 3 highest

PX2H:

If set, Set priority for external interrupt 2 highest

PT2H:

If set, Set priority for timer2 interrupt highest

PSH:

If set, Set priority for serial port interrupt highest

PT1H:

If set, Set priority for timer1 interrupt highest

PX1H:

If set, Set priority for external interrupt 1 highest

PT0H:

If set, Set priority for timer0 interrupt highest

PX0H:

If set, Set priority for external interrupt 0 highest

MEGAWIN

MPC89x53A Data Sheet

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