Section 9 16-Bit Timer Pulse Unit (TPU)
9.9.3
Caution on Cycle Setting
When counter clearing by compare match is set, TCNT is cleared in the final state in which it
matches the TGR value (the point at which the count value matched by TCNT is updated).
Consequently, the actual counter frequency is given by the following formula:
f =
(N + 1)
f:
Counter frequency
Pφ:
Operating frequency
N:
TGR set value
9.9.4
Conflict between TCNT Write and Clear Operations
If the counter clearing signal is generated in the T2 state of a TCNT write cycle, TCNT clearing
takes precedence and the TCNT write is not performed. Figure 9.47 shows the timing in this case.
Rev. 3.00 Mar. 14, 2006 Page 338 of 804
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Pφ
Pφ
Address
Write
Counter clear
signal
TCNT
Figure 9.47 Conflict between TCNT Write and Clear Operations
TCNT write cycle
T1
T2
TCNT
address
N
H'0000