UPD784938 Datasheet, PDF (344/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 11 TIMER/EVENT COUNTER 2
If a value equal to or less than the TM2 value is written to CR20 before the CR20 and TM2 match, the duty of that
PPG cycle will be 100%. CR20 rewriting should be performed by the interrupt due to a match between TM2 and CR20.
Figure 11-32. Example of 100% Duty with PPG Output
CR21
CR21
CR21
CR21
TM2
count value
0H
n1
n1
n3
n2
n2
n2
CR20
n1
n2
TO2
When value n2 which is smaller than the TM2 value n3 is
written to CR20 here, the duty of this period will be 100%.
Remark ALV2 = 0
Caution If the PPG cycle is extremely short as compared with the time required to acknowledge an interrupt,
the value of CR20 cannot be rewritten by interrupt processing that is performed on match between
TM2 and CR20. Use another method (for example, to poll the interrupt request flags by software
with all the interrupts masked).
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Preliminary User’s Manual U13987EJ1V0UM00