3822 datasheet(102/328 Pages) RENESAS

102 / 328 page

APPLICATION

2.3 Timer X and timer Y

3822 GROUP USER’S MANUAL

2–36

(3) Event counter mode

The operation in the event counter mode is the same as that in the timer mode except that the input

signal to the CNTR0 pin is used as a count source.

Operation in the event counter mode is described below.

Start of count operation

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

count operation is automatically started after reset release.

The value of the X counter is decremented by 1 each time a count source is input.

As an active edge, the falling edge ( ) or rising edge ( ) is specified by the CNTR0 active edge

switch bit.

Reload operation

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

At this time, the value of the X latch is transferred (reloaded) to the X counter.

Interrupt operation

sCounter underflow

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

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

bit.

sEdge of count source

At the edge of the count source input from the P54/CNTR0 pin, an interrupt request occurs. At the

same time, the CNTR0 interrupt request bit is set to “1.” The occurrence of an interrupt is controlled

by the CNTR0 interrupt enable bit.

As an active edge, the falling edge ( ) or rising edge ( ) is specified by the CNTR0 active edge

switch bit.

Stop of count operation

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

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

Figure 2.3.3 shows an event counter mode operation example.

3822 Datasheet(PDF) 102 Page - Renesas Technology Corp