7540 datasheet(110/366 Pages) RENESAS

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2-34

REJ09B0018-0200Z

Rev.2.00

Jun 21, 2004

APPLICATION

7540 Group

2.2 Timer A

Fig. 2.2.26 Example of control procedure (2)

CNTR1 interrupt processing routine

T h e n u m b e r o f u n d e rflo w is w ith in th e ra n g e ?

(“1 2 ” o r m o re a n d le ss th a n “4 3 ”)

When judging that a ringing pulse exists as

a result of several period measurement, set

“1” to the ringing flag.

Set “0” to the “H” width decision flag and

the “L” width decision flag.

* Error processing

When P00/CNTR1 = “0”,

“H” duration measuring is finished.

* Error processing

Set “1” to the unusual value detection flag

RTI

T h e n u m b e r o f a p e rio d ’s

u n d e rflo w is w ith in th e ra n g e ?

(“2 0 ” o r m o re a n d le ss th a n “5 9 ”)

Timer A interrupt processing routine

Count the number of underflows

RTI

Set “1” to the “L” width decision flag.

Set “1” to the “H” width decision flag.

T h e n u m b e r o f u n d e rflo w is w ith in th e ra n g e ?

(“4 ” o r m o re a n d le s s th a n “2 3 ”)

L e v e l o f P 00/C N T R 1 is c h e cke d , a n d w h ich

d u ra tio n m e a su rin g is fin is h e d is ju d g e d .

When P00/CNTR1 = “1”,

“L” duration measuring is finished.

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