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CHAPTER 8 PULSE WIDTH COUNT TIMER (PWC)
8.1
Overview of Pulse Width Count Timer
The pulse width count timer (PWC) can be selected to function as either an interval
timer or the pulse width measurement. The interval timer function counts down in
synchronous with one of three internal count clocks. The pulse width measurement
function measures the width of pulses input to an external pin.
Therefore, the PWC can be used as an input capture by continuously measuring the
pulse width of an external input.
I Interval timer function
The interval timer function generates repeated interrupts at variable time intervals.
• The interval timer can operate with a cycle among 1 and 2
• The internal count clock can be selected from three different clocks.
• Two operating modes are available: reload timer mode (continuous operation) and one-shot mode (one-
time operation).
Table 8.1-1 "Interval time range" lists the available interval time and square wave output ranges.
Table 8.1-1 Interval time range
Internal count clock cycle
t
: Instruction cycle (divide-by-four main clock oscillation)
inst
The following shows an example of the interval time.
For a 5 MHz main clock oscillation (F
and a count clock cycle of one instruction cycle, the interval time and square wave output frequency are
calculated as follows:
142
1 t
inst
4 t
inst
32 t
inst
CH
Interval time
= (1 x 4/F
= (4/5 MHz) x 221
= 176.8 s
RLBR register value of "00
8
times the internal count clock cycle.
Interval time
8
1 t
to 2
t
inst
inst
2
10
2
t
to 2
t
inst
inst
5
13
2
t
to 2
t
inst
inst
), a PWC reload buffer register (RLBR) value of "DD
) x (RLBR register value)
CH
" is assumed as 256.
H
Square wave output (Hz)
9
1/(2 t
) to 1/(2
t
)
inst
inst
3
11
1/(2
t
) to 1/(2
t
)
inst
inst
6
14
1/(2
t
) to 1/(2
t
)
inst
inst
H
(221)",
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