MC68HC908LB8_05 Datasheet, PDF (95/234 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Functional Description
1 CYCLE
10 kHz
20 kHz
0
10
20
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50
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90
% CYCLE
100
10 kHz
20 kHz
t
13 kHz
AVERAGE
SIGNAL
Figure 10-4. Dithering Waveforms
10.4.2 Frequency Dithering on the HRP
The HRP provides frequency dithering between two signals whose periods differ by one HRPCLK cycle.
When the HRP is supplied with an 8 MHz clock, the difference between the period values is 125 ns.
The HRP provides a programmable number of dithering steps, up to a maximum of 32 steps. This results
in a maximum frequency resolution of 125/32 = 3.906 ns when using an 8 MHz clock.
Figure 10-5 shows the relationship between the two dithering frequencies and the output frequency when
32 dithering steps are chosen. In this example, the Period signal is output for 25% of the time, i.e. 8 of the
32 steps, and the Period+1 signal is output for 75% of the time, i.e. 24 of the 32 steps.
MC68HC908LB8 Data Sheet, Rev. 1
Freescale Semiconductor
95