M38203M4 Datasheet, PDF (122/344 Pages) Mitsubishi Electric Semiconductor – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.3 Timer X and timer Y
(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 P54/CNTR0 pin is used as a count source.
Operation in the event counter mode is described below.
xStart 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.
ŽInterrupt 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.
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3820 GROUP USER’S MANUAL