NEC PD78214 - Manual (Page 219)

190
µ
PD78214 Sub-Series
7.3.11 Sample Applications
(1) Interval timer operation (1)
By free running 8-bit timer 2 (TM2), and adding a value to a compare register (CR20, CR21) in an interrupt
handling routine, 8-bit timer/counter 2 can be used as an interval timer whose period is as long as the added
value. (See Fig. 7-96.)
In addition, 8-bit timer 2 (TM2) has two compare registers, so that interval timers with two types of periods
can be produced.
Fig. 7-97 shows the setting of control registers. Fig. 7-98 shows the setting procedure. Fig. 7-99 shows
interrupt handling.
Fig. 7-96 Timing of Interval Timer Operation (1)
n
n
0H
TM2
count value
MOD(2n)
MOD(3n)
FFH
MOD(2n) MOD(3n) MOD(4n)
Timer starts
Compare register
(CR20)
INTC20
interrupt request
Rewriting by inter-
rupt program
Interval Interval Interval
Rewriting by inter-
rupt program Rewriting by inter-
rupt program
FFH
Remark Interval = n × x/f
CLK
, 1 ≤ n ≤ FFH
x = 16, 32, 64, 128, 256, 512