3822 datasheet(108/328 Pages) RENESAS

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APPLICATION

2.3 Timer X and timer Y

3822 GROUP USER’S MANUAL

2–42

2.3.2 Explanation of timer Y operations

Timer Y has 4 modes of operation.

Operation in each mode is described below.

(1) Timer Mode

Operation in the timer mode is described below.

Start of count operation

Immediately after reset release, the timer Y stop control bit is in the “0” state. For this reason, the

count operation is automatically started after reset release.

The value of the timer Y counter (referred as “the Y counter”) is decremented by 1 each time a

count source is input.

The count source is f(XIN)/16 clock (low-speed mode ; f(XCIN)/16 clock).

Reload operation

The Y counter underflows at the first count pulse after the value of the Y counter reaches “0016.”

At this time, the value of the timer Y latch (referred as “the Y latch”) is transferred (reloaded) to the

Y counter.

Interrupt operation

An interrupt request occurs at the Y counter underflow. At the same time, the timer Y interrupt

request bit is set to “1.” The occurrence of an interrupt is controlled by the timer Y interrupt enable

bit.

An interrupt request occurs each time the counter underflows. In other words, an interrupt request

occurs every “the Y counter initial value + 1” count of the rising edge of the count source.

Stop of count operation

By writing “1” to the timer Y stop control bit by software, the count operation is stopped.

The count operation is continued until “1” is set to the timer Y stop control bit.

Figure 2.3.6 shows a timer mode operation example.

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