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5 tcnt external reset timing, 6 timing of overflow flag (ovf) setting – Renesas H8S/2111B User Manual

Page 243

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Rev. 1.00, 05/04, page 209 of 544

10.5.5 TCNT

External Reset Timing

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 width of the clearing pulse must be at least 1.5 states. Figure
10.10 shows the timing of clearing the counter by an external reset input.

φ

Clear signal

External reset
input pin

TCNT

N

H'00

N – 1

Figure 10.10 Timing of Counter Clear by External Reset Input

10.5.6 Timing

of

Overflow Flag (OVF) Setting

The OVF bit in TCSR is set to 1 when the TCNT overflows (changes from H'FF to H'00). Figure
10.11 shows the timing of OVF flag setting.

φ

OVF

Overflow signal

TCNT

H'FF

H'00

Figure 10.11 Timing of OVF Flag Setting

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