NEC PD75402A Manuale Utente

In this example the basic interval timer is enabled, and the interrupt generation interval is set to 1.95

ms (at 4.19 MHz operation).

SEL

MB15

MOV

A, #1111B

MOV

BTM,A

; Setting and start

EI

; Enable interrupts

EI

IEBT

; Enable BT interrupts

Example of watchdog timer application

When used as a watchdog timer, the basic interval timer’s function of generating an interrupt (INTBT)

at set intervals is used.

First, the standard time generated by the basic interval timer is decided.

Next, the program is divided into a number of modules whose processing should terminate within

the standard time, and the counter (BT) and interrupt request flag (IRQBT) are cleared each time a

module ends. A program is written such that an interrupt (INTBT) is not generated if operation is

normal. In other words, if an interrupt is generated, this is interpreted as indicating inadvertent

program looping.

The interrupt generation interval is set to 31.25 ms (in 4.19 MHz operation) so that the processing

time for each module is less than 31.25 ms.

Initial

Setting

➤

MOV A, #1011B

MOV BTM, A

Module 1

Processing termination within 31.25 ms

➤

➤

MOV A, #1011B

MOV BTM, A

Module 2

Processing termination within 31.25 ms

➤

SEL

MB15

; or CLR1 MBE

MOV

A, #1011B

MOV

BTM, A

; Interval setting and counter start

EI

EI

IEBT

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