NEC PD78058FY(A) - Manual (Page 237)

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CHAPTER 9 8-BIT TIMER/EVENT COUNTERS
Count Pulse
CR10, CR20
TM1, TM2 Count Value X-1 X FFH 00H 01H 02H
M N
(3) Operation after compare register change during timer count operation
If the values after the 8-bit compare registers 10 and 20 (CR10 and CR20) are changed are smaller than those
of 8-bit timer registers (TM1 and TM2), TM1 and TM2 continue counting, overflow and then restart counting
from 0. Thus, if the value (M) after CR10 and CR20 change is smaller than value (N) before the change, it
is necessary to restart the timer after changing CR10 and CR20.
Figure 9-16. Timing After Compare Register Change During Timer Count Operation
Remark N
>
X
>
M