UPD17072 datasheet(95/228 Pages) RENESAS

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µPD17072,17073

12.3.2 Application example of basic timer 1

A program example is shown below.

Example

MEM

0.10H

; 80-ms counter

BTIMER1 DAT

0002H

; Symbol definition of basic timer 1 interrupt vector address

START

; Branches to START

ORG

BTIMER1

; Program address (0002H)

ADD

M1, #0001B

; Adds 1 to M1

SKT1

; Tests CY flag

EI_RETI

; Returns if no carry

MOV

M1, #0110B

Processing A

EI_RETI:

RETI

START:

MOV

M1, #0110B

; Initializes contents of M1 to 6

BANK1

SET1

BTM1CK

; Embedded macro

; Sets basic timer 1 interrupt pulse to 8 ms

SET1

IPBTM1

; Enables basic timer 1 interrupt

; Enables all interrupts

LOOP:

BANK0

Processing B

LOOP

This program executes processing A every 80 ms.

The points to be noted in this case are that the DI status is automatically set when an interrupt has been accepted,

and that the IRQBTM1 flag is set to 1 even in the DI status.

This means that the interrupt is accepted even if execution exits from an interrupt service routine by execution of

the “RETI” instruction, if processing A takes longer than 8 ms.

Consequently, processing B is not executed.

UPD17072 Datasheet(PDF) 95 Page - Renesas Technology Corp

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