INTERRUPTS

KS57C2308/P2308/C2316/P2316

 

 

+PROGRAMMING TIP — Setting the INT Interrupt Priority

The following instruction sequence sets the INT1 interrupt to high priority:

BITS

EMB

 

 

SMB

15

 

 

DI

;

IPR.3 (IME)

0

LD

A,#3H

 

 

LD

IPR,A

 

 

EI

;

IPR.3 (IME)

1

EXTERNAL INTERRUPT 0 AND 1 MODE REGISTERS (IMOD0 and IMOD1)

The following components are used to process external interrupts at the INT0 and INT1 pins:

Noise filtering circuit for INT0

Edge detection circuit

Two mode registers, IMOD0 and IMOD1

The mode registers are used to control the triggering edge of the input signal. IMOD0 and IMOD1 settings let you choose either the rising or falling edge of the incoming signal as the interrupt request trigger. The INT4 interrupt is an exception since its input signal generates an interrupt request on both rising and falling edges. Since INT2 is a qusi-interrupt, the interrupt request flag (IRQ2) must be cleared by software.

FB4H

IMOD0.3

"0"

IMOD0.1

IMOD0.0

 

 

 

 

 

FB5H

"0"

"0"

"0"

IMOD1.0

 

 

 

 

 

FB6H

"0"

IMOD2.2

IMOD2.1

IMOD2.0

 

 

 

 

 

IMOD0, IMOD1 and IMOD2 are addressable by 4-bit write instructions. RESET clears all IMOD values to logic zero, selecting rising edges as the trigger for incoming interrupt requests.

 

 

Table 7-5. IMOD0 and IMOD1 Register Organization

 

 

 

 

 

 

IMOD0

IMOD0.3

0

IMOD0.1

IMOD0.0

Effect of IMOD0 Settings

 

 

 

 

 

 

 

0

 

 

 

Select CPU clock for sampling

 

 

 

 

 

 

 

1

 

 

 

Select fxx/64 sampling clock

 

 

 

 

 

 

 

 

 

0

0

Rising edge detection

 

 

 

 

 

 

 

 

 

0

1

Falling edge detection

 

 

 

 

 

 

 

 

 

1

0

Both rising and falling edge detection

 

 

 

 

 

 

 

 

 

1

1

IRQ0 flag cannot be set to "1"

 

 

 

 

 

 

IMOD1

0

0

0

IMOD1.0

Effect of IMOD1 and IMOD2 Settings

 

 

 

 

 

0Rising edge detection

1Falling edge detection

7-8

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Image 192
Samsung KS57C2308 manual IMOD0 IMOD0.3 IMOD0.1 IMOD0.0, IMOD1 IMOD1.0