7477 datasheet(250/354 Pages) RENESAS

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2-15

7470/7471/7477/7478 GROUP USER’S MANUAL

APPLICATION

2.3 Timers

7470

7471

7477

7478

Fig. 2.3.4 Example of control procedure [Frequency measurement]

RTI

RTS

Frequency measurement routine

Clear the timer 2 interrupt enable bit

(Timer 2 interrupt disabled)

Set the Timer 12 mode register

!! !

!! 1 !

Timer 1 count stop

Timer 2 count stop

Set the Timer 12 mode register

! 1

10 1 !

Timer 1 count source

← CNTR0

Timer 2 count source

← Internal clock

Timer 2 internal clock count source

←f(XIN)/64

Set the Edge polarity selection register

1 !

!!! !

! EG (Address 00D416)

CNTR0 rising edge selected

Set the Timer 1 to “FF 16”

Set the Timer 2 to “7C 16”

Clear the timer 2 interrupt request bit

Set the timer 2 interrupt enable bit

(Timer 2 interrupt enabled)

Set the Timer 12 mode register

! 1

10 0 !

Timer 1 count start

Timer 2 count start

Timer 2 interrupt

Read timer 1

Set the Timer 12 mode register

! 1

10 1 !

1 T12M (Address 00F816)

Timer 1 count stop

Timer 2 count stop

According to required accuracy, the event count

value within 1 ms is detected repeatedly, and its

results are averaged.

(Timer 1 set value FF 16) – (Timer 1 read value)

← Event count value within 1 ms

T12M (Address 00F8 16)

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