4501 datasheet(146/212 Pages) RENESAS

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2.3 Timers

2-29

4501 Group

APPLICATION

Rev.2.01

Feb 07, 2005

REJ09B0192-0201

Fig. 2.3.6 Timer start by external input setting example (1)

b3b0

➀ Disable Interrupts

Timer 1 interrupt and INT interrupt are temporarily disabled.

Interrupt enable flag INTE

Interrupt control register V1

“0”

✕✕

All interrupts disabled (DI instruction)

Timer 1 interrupt occurrence disabled

(TV1A instruction)

INT interrupt occurrence disabled

0 1

➂ Stop Timer Operation

Timer 1 and prescaler are temporarily stopped.

Dividing ratio of prescaler is selected.

Timer control register W1

Timer 1 stop (TW1A instruction)

Prescaler stop

Prescaler divided by 16 selected

Count start synchronous circuit selected

➄ Set Timer Value

Timer 1 count time is set.

Timer 1 reload register R1 “5216”

Timer count value 82 set (T1AB instruction)

➃ Set Port

P13/INT pin is set to INT input.

Port P13 output latch

✕ ✕

Input mode is set (OP1A instruction)

➅ Clear Interrupt Request

Timer 1 interrupt activated condition is cleared.

Timer 1 interrupt request flag T1F “0”

Timer 1 interrupt activated condition cleared

(SNZT1 instruction)

Note when the interrupt request is cleared

When ➅ is executed, considering the skip of the next instruction according to the

interrupt request flag T1F, insert the NOP instruction after the SNZT1 instruction.

➁ Initialize valid waveform

INT pin is initialized.

INT pin input disabled, Timer 1 control disabled.

Interrupt control register I1

INT pin input disabled (TI1A instruction)

Timer 1 control disalbed

1 1

➆ Start Timer Operation

Timer 1 and prescaler temporarily stopped are restarted.

Timer control register W1

Timer 1 operating (TW1A instruction)

Prescaler operating

Continue to Figure 2.3.7 on the next page.

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