Notes On Using 8-Bit Timer/Event Counters - NEC UPD789026 Series User Manual

7.5 Notes on Using 8-Bit Timer/Event Counters

(1) Error on starting timer
An error of up to 1 clock occurs after the timer has been started until a coincidence signal is generated.
This is because 8-bit timer counter 00 (TM00) started asynchronously with the count pulse.
Count Pulse
TM00 Count Value
(2) Setting of 8-bit compare register
8-bit compare register 00 (CR00) can be set to 00H.
Therefore, one pulse can be counted when an 8-bit timer/event counter operates as an event counter.
TI0 Input
TM00 Count Value
Interrupt Request Flag
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CHAPTER 7 8-BIT TIMER/EVENT COUNTER
Figure 7-7. 8-Bit Timer Counter 00 Start Timing
00H
Timer starts
Figure 7-8. External Event Counter Operation Timing
CR00
User's Manual U11919EJ3V0UM00
01H 02H
00H
00H 00H
03H 04H
00H 00H