Notes On Using 8-Bit Timers 50, 60 - NEC UPD789426 Series User Manual

7.5 Notes on Using 8-Bit Timers 50, 60

(1) Error on starting timer
An error of up to 1 clock is included in the time between the timer being started and a match signal being
generated. This is because 8-bit timer counter n0 (TMn0) is started asynchronously to the count pulse.
Count pulse
TMn0
count value
Remark n = 5, 6
(2) Setting of 8-bit compare register n0
8-bit compare register n0 (CRn0) can be set to 00H.
Therefore, one pulse can be counted when the 8-bit timer operates as an event counter.
Remark n = 5, 6
Figure 7-29. Timing of Operation as External Event Counter (8-Bit Resolution)
TMI60 input
CR60
TM60
count value
Interrupt request flag
176
CHAPTER 7 8-BIT TIMERS 50, 60
Figure 7-28. Start Timing of 8-Bit Timer Counter
00H 01H
Timer start
00H
User's Manual U15075EJ2V1UD
02H 03H
00H
00H 00H
04H
00H