NEC PD78214 - Manual (Page 158)

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Chapter 7 Timer/Counter Units
7
7.1.9 Sample Applications
(1) Interval timer operation (1)
By free running 16-bit timer 0 (TM0), and adding a value to a compare register (CR00, CR01) in an interrupt
handling routine, the 16-bit timer/counter can be used as an interval timer whose period is as long as the added
value. (See Fig. 7-24.)
This interval timer has a resolution of 1.3 µs, and can count up to 87.4 ms (at internal system clock f
CLK
= 6
MHz).
In addition, 16-bit timer 0 (TM0) has two compare registers, so that interval timers with two types of periods
can be produced.
Fig. 7-25 shows the setting of control registers. Fig. 7-26 shows the setting procedure. Fig. 7-27 shows
interrupt handling.
Fig. 7-24 Timing of Interval Timer Operation (1)
n
n
0H
TM0
count value
MOD(2n)
MOD(3n)
FFFFH FFFFH
MOD(2n) MOD(3n) MOD(4n)
Timer starts
Compare register
(CR00)
INTC00
interrupt request
Rewriting by inter-
rupt program
Interval Interval Interval
Rewriting by inter-
rupt program Rewriting by inter-
rupt program
Remark Interval = n × 8/f
CLK
, 1 ≤ n ≤ FFFFH