7480 datasheet(117/337 Pages) RENESAS

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7480 Group and 7481 Group User's Manual

1-100

HARDWARE

1.13 Timer 1 and Timer 2

Writes to and Reads from Timer

When ‘TL (0016 through FF16)’ is written to a timer, ‘TL’ is set in both the timer and the timer latch

( in Figure 1.13.7).

Also, the contents of the timer can be read by a read operation.

Count Operation

• When the timer 1 or 2 stop control bit is cleared to ‘0’, the timer starts counting ( in Figure 1.13.7).

• When the timer 1 or 2 stop control bit is set to ‘1’, the timer stops counting ( in Figure 1.13.7).

In the count operation, the contents of each timer are decremented by 1 at every rising edge of the

count source ( in Figure 1.13.7).

Reloading Timers

When a timer reaches ‘FF16’ in the count operation, an underflow occurs at the subsequent rising

edge of the count source, and the value decremented by 1 from the contents of the timer latch is

reloaded to the timer. ( in Figure 1.13.7).

Timer Interrupt

At an underflow, the timer 1 or 2 interrupt request bit is set to ‘1’; then a timer interrupt request is

generated ( in Figure 1.13.7).

FF16

0016

Count source

Timer 1 stop

control bit

Timer 1 interrupt

request bit

‘0’ is

written

‘0’ is

written

‘1’ is

written

Writing to timer 1

Count start

Count stop

Count start

: Setting value to timer 1

: The value which is the timer latch decremented by 1 is reloaded

: Underflow

: Count period

: Clearing by writing ‘0’ to interrupt request bit or accepting interrupt request

Count source frequency

× (Setting value to timer 1 +1)

Writing to timer 1

Time

T(s) =

TL–1

Figure 1.13.7 Operations in Timer Mode

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