CHAPTER 7 TIMER/COUNTER FUNCTION
User’s Manual U13850EJ6V0UD
252
7.4.6 Cautions
(1) Error when the timer starts
An error of up to 1 clock occurs in the time until the match signal is generated after the timer starts. The reason
is that 8-bit counter n (TMn) starts asynchronous to the count pulse.
Figure 7-38. Start Timing of Timer n
Remark
n = 2 to 7
(2) Operation after compare register is changed while timer is counting
If the value after 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 after CRn0
changes (M) is less than the value before the change (N) and less than the count value of the TMn register, the
timer must restart after CRn0 changes (n = 2 to 5).
Figure 7-39. Timing After Compare Register Changes During Timer Count Operation
TMn count value
N
Count pulse
CRn0
X
−
1
X
FFH
00H
01H
02H
M
Remarks 1.
N > X > M
2.
n = 2 to 7
Caution
Except when the TIm input is selected, always set TCEn = 0 before setting the stop state (m = 2
to 5).
(3) TMn read out during timer operation
Since reading out TMn during operation occurs while the selected clock is temporarily stopped, select a high-or
low-level waveform that is longer than the selected clock (n = 2 to 7).
00H
01H
02H
03H
04H
↑
Timer starts
TMn count value
Count pulse
Содержание V850/SB1
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