536
13.3.3
Timing of External RESET on TCNT
TCNT is cleared at the rising edge of an external reset input, depending on the settings of the
CCLR1 and CCLR0 bits in TCR. The clear pulse width must be at least 1.5 states. Figure 13-7
shows the timing of this operation.
ø
Clear signal
External reset
input pin
TCNT
N
H'00
N–1
Figure 13-7 Timing of External Reset
13.3.4
Timing of Overflow Flag (OVF) Setting
The OVF in TCSR is set to 1 when the timer count overflows (changes from H'FF to H'00). Figure
13-8 shows the timing of this operation.
ø
OVF
Overflow signal
TCNT
H'FF
H'00
Figure 13-8 Timing of OVF Setting