CHAPTER 7 TIMER/COUNTER FUNCTION
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7.4.5 Cautions
(1) Error when the timer starts
The time until the coincidence signal is generated after the timer starts has a maximum error of one clock. The
reason is the starting of the 8-bit counter n (TMn) is asynchronous with respect to the count pulse.
Figure 7-43. Start Timing of Timer n
Remark
n = 2 to 5
(2) Operation after the compare register is changed while the timer is counting
If the value after the 8-bit compare register n (CRn0) changes is less than the value of the 8-bit timer register
(TMn), counting continues, overflows, and counting starts again from 0. Consequently, when the value (M) after
CRn0 changes is less than the value (N) before the change, the timer must restart after CRn0 changes.
Figure 7-44. Timing After Compare Register Changes During Timer Counting
N
M
Count pulse
CRn0
X
X-1
FFH
00H
01H
02H
TMn count value
Remarks 1.
N > X > M
2.
n = 2 to 5
Caution
Except when the TIn input is selected, always set TCEn = 0 before setting the stop state.
(3) TMn read out during timer operation
Since reading out TMn during operation occurs while the selected clock is temporarily stopped, select some high
or low level waveform that is longer than the selected clock.
00H
01H
02H
03H
04H
↑
Timer starts
TMn count value
Count pulse
Содержание V850/SA1 mPD703015
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