HD6433308 Datasheet, PDF (189/349 Pages) Hitachi Semiconductor – Hitachi Single-Chip MicroComputer

Resolution =
PWM period
PWM frequency
1/clock source frequency
= resolution × 250
= 1/PWM period
If the system clock frequency is 10MHz, then the resolution, period, and frequency of the PWM
output for each clock source are given in Table 8-3.
Table 8-3. PWM Timer Parameters for 10MHz System Clock
Internal clock frequency
Ø/2
Ø/8
Ø/32
Ø/128
Ø/256
Ø/1024
Ø/2048
Ø/4096
Resolution
200ns
800ns
3.2µ s
12.8µ s
25.6µ s
102.4µ s
204.8µ s
409.6µ s
PWM period
50µ s
200µ s
800µ s
3.2ms
6.4ms
25.6ms
51.2ms
102.4ms
8.3 Operation
PWM frequency
20kHz
5kHz
1.25kHz
312.5Hz
156.3Hz
39.1Hz
19.5Hz
9.8Hz
8.3.1 Timer Incrementation
The PWM clock source is created from the system clock (Ø) by a prescaler. The timer counter
increments on a TCNT clock pulse generated from the falling edge of the prescaler output as shown
in Figure 8-2.
Ø
Prescaler
output
TCNT clock
pulse
TCNT
N–1
N
N+1
Figure 8-2. TCNT Increment Timing
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