HD6433308 Datasheet, PDF (155/349 Pages) Hitachi Semiconductor – Hitachi Single-Chip MicroComputer

Ø
Prescaler
output
FRC clock
pulse
FRC
N –1
N
N+1
Figure 6-5. Increment Timing for Internal Clock Source
If external clock input is selected, the FRC increments on the rising edge of the FTCI clock signal.
Figure 6-6 shows the increment timing.
The pulse width of the external clock signal must be at least 1.5 system clock (Ø) periods. The
counter will not increment correctly if the pulse width is shorter than one Ø period.
Ø
FTCI
FRC clock pulse
FRC
N
N+1
Figure 6-6. Increment Timing for External Clock Source
Ø
FTCI
Figure 6-7. Minimum External Clock Pulse Width
140