7477 datasheet(248/354 Pages) RENESAS

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2-13

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

APPLICATION

2.3 Timers

7470

7471

7477

7478

Fig. 2.3.2 Example of control procedure [Clock function]

RESET

RTI

Initialization

Set the interrupt disable flag (each interrupt disabled)

Clear the timer 1 interrupt enable bit

(timer 1 interrupt disabled)

Set the timer 12 mode register

1 0

!! !!

Timer 1 count stop

Timer 1 count source

← Internal clock

Timer 1 internal clock count source

← f(XCIN)

Set the CPU mode register

!! 0

! 11 !

Fixed to “0”

Select XCIN, XCOUT

XCOUT drive capacity

← High power

Wait the f(XCIN) oscillation stabilizing time

Set the Timer 1 to “7F 16”

Set the Timer 12 mode register

1 0

!! !!

0 T12M (Address 00F816)

Timer 1 count start

Clear the timer 1 interrupt request bit

Set the timer 1 interrupt enable bit

(Timer 1 interrupt enabled)

Clear the interrupt disable flag (each interrupt enabled)

Clock stop ?

1 second has elapsed ?

(1 second counter = 250 ?)

Clear 1 second counter

Clock count up (second–year)

Clear 1 second counter

Set the Timer 1 to “7F 16”

Clear the Timer 1 interrupt request bit

Processing for timer

set is completed ?

Timer 1 interrupt

1 second counter + 1

Interrupt at every 0.4 ms

q For concrete time, ask the oscillator manufacture for information.

Count by interrupt processing

q 1 second = 1/32 kHz ! (127+1) ! 250

Dividing ratio

7F16

When re-starting the clock from zero second

after completing to set the clock, set timers again.

Set the timer so that every processing within the loop marked

may

be executed in a period of 1 second or less.

T12M (Address 00F8 16)

CPUM (Address 00FB 16)

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