IBM uPD78082 - Manual (Page 124)

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CHAPTER 6 8-BIT TIMER/EVENT COUNTERS 5 AND 6
Count Pulse
CR50, CR60
TM5, TM6 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 50 and 60 (CR50 and CR60) are changed are smaller than those
of 8-bit timer registers 5 and 6 (TM5 and TM6), TM5 and TM6 continue counting, overflow and then restart
counting from 0. Thus, if the value (M) after CR50 and CR60 change is smaller than value (N) before the
change, it is necessary to restart the timer after changing CR50 and CR60.
Figure 6-20. Timing after Compare Register Change during Timer Count Operation
Remark N > X > M