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CHAPTER 8 8-BIT TIMER/EVENT COUNTERS 2 TM2 AND 3 TM3
Preliminary User’s Manual U14581EJ3V0UM00
8.5 8-Bit Timer/Event Counters 2 TM2 and 3 TM3 Cautions
(1) Timer start errors
An error with a maximum of one clock may occur concerning the time required for a match signal to be generated
after timer start. This is because 8-bit counters 2 and 3 (TM2 and TM3) is started asynchronously with the count
pulse.
Figure 8-11. 8-Bit Counters 2 and 3 (TM2 and TM3) Start Timing
Count pulse
TMn count value
00H
01H
02H
03H
04H
Timer start
Remark
n = 2, 3
(2) Operation after compare register change during timer count operation
If the values after the 8-bit compare registers 2 and 3 (CR2 and CR3) are changed are smaller than the value
of 8-bit counters 2 and 3 (TM2 and TM3), TM2 and TM3 continue counting, overflow and then restart counting
from 0. Thus, if the value (M) after CR2 and CR3 change is smaller than value (N) before the change, it is
necessary to restart the timer after changing CR2 and CR3.
Figure 8-12. Timing after Compare Register Change during Timer Count Operation
Count pulse
CRn
TMn count value
N
M
X – 1
X
FFH
00H
01H
02H
Remarks 1.
N > X > M
2.
n = 2, 3
(3) TM2 and TM3 reading during timer operation
When TM2 and TM3 are read during operation, choose a select clock which has a longer high/low level wave
because the select clock is stopped temporarily.
Содержание mPD780851
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