Timer A
M30240 Group
Rev.1.00 Sep 24, 2003 Page 142 of 360
2.2 Timer A
2.2.1 Overview
The following is an overview for Timer A, a 16-bit timer.
2.2.1.1 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
function that reverses output from a port every time an overflow occurs, or the gate function which con-
trols the count start/stop according to the input signal from a port.
(b) Event counter mode
This mode counts the pulses from an external signal 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 A2, A3 and A4 have a 2-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.
(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 3 types: an external input signal, 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.
• Timer mode operation See section 2.2.2.1
• Timer mode, gate function operation See section 2.2.2.2
• Timer mode, pulse output function operation See section 2.2.2.3
• Event counter mode, reload type operation
See section 2.2.2.4
• Event counter mode, free run type operation
See section 2.2.2.5
• Operation of the 2-phase pulse signal processing
function in normal event counter mode
See section 2.2.2.6
• Operation of the 2-phase pulse signal processing
function in 4-multiplication mode
See section 2.2.2.7
• Operation in one-shot timer mode effected by software
See section 2.2.2.8
• Operation in one-shot timer mode effected by an
external trigger
See section 2.2.2.9
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