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2.2 Timer A
2.2.1 Overview
The following is an overview for timer A, a 16-bit timer.
(1) Mode
Timer A operates in one of the four modes:
(a) Timer mode
In this mode, the internal count source is counted. Two functions can be selected: the pulse output
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function that reverses output from a port every time an overflow occurs, or the gate function which
controls the count start/stop according to the input signal from a port.
(b) Event counter mode
This mode counts the pulses from the outside and the number of overflows in other timers. The free-
run type, in which nothing is reloaded from the reload register, can be selected when an underflow
occurs. The pulse output function can also be selected. Please refer to the timer mode explanation
for details, as the operation is identical.
Furthermore, Timer A has a two-phase pulse signal processing function which generates an up
count or down count in the event counter mode, depending on the phase of the two input signals.
The normal mode or 4-multiplication mode can be selected depending on the phase detective
method.
(c) One-shot timer mode
In this mode, the timer is started by the trigger and stops when the timer goes to "0". The trigger can
be selected from the following 2 types: an overflow of the timer, or a software trigger. The pulse
output function can also be selected. Please refer to the timer mode explanation for details, as the
operation is identical.
(d) Pulse width modulation (PWM) mode
In this mode, the arbitrary pulses are successively output. Either a 16-bit fixed-period PWM mode or
8-bit variable-period mode can be selected. The trigger for initiating output can also be selected.
Please refer to the one-shot timer mode explanation for details, as the operation is identical.
(2) Count source
The internal count source can be selected from f
dividing the CPU's main clock by 1, 8, and 32 respectively. Clock f
secondary clock by 32.
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
page 6 of 354
, f
, f
, and f
. Clocks f
1
8
32
C32
is derived by dividing the CPU's
C32
2. Timer A
, f
, and f
are derived by
1
8
32
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