3822 datasheet(110/328 Pages) RENESAS

110 / 328 page

APPLICATION

2.3 Timer X and timer Y

3822 GROUP USER’S MANUAL

2–44

(2) Period measurement mode

In the period measurement mode, the period of a pulse input from the P55/CNTR1 pin is measured.

Operation in the period measurement 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 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

At the edge of the pulse input from the P5 5/CNTR1 pin, the value of the Y latch is transferred

(reloaded) to the Y counter. The count value immediately before reload is held until it is read out

once after reload.

As an active edge, the falling edge (

) or rising edge (

) is specified by the CNTR1 active edge

switch bit.

The value of the Y latch is also reloaded at the Y counter underflow.

Period measurement

As a period measurement duration, the following is selected by the CNTR1 active edge switch

bit (bit 6) : Duration from the falling edge to the falling edge (bit 6 = “0”)

Duration from the rising edge to the rising edge (bit 6 = “1”)

The difference between the count value at an active edge input and that immediately before reload

is a measured period.

Interrupt operation

sEdge of input pulse

At the edge of the pulse input from the P55/CNTR1 pin, an interrupt request occurs. At the same

time, the CNTR1 interrupt request bit is set to “1.” The occurrence of an interrupt is controlled by

the CNTR1 interrupt enable bit.

As an active edge, the falling edge ( ) or rising edge ( ) is specified by the CNTR1 active edge

switch bit.

sCounter underflow

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.

Figure 2.3.7 shows a period measurement mode operation example.

3822 Datasheet(PDF) 110 Page - Renesas Technology Corp