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25.2.2
Frequency Data register
The Frequency Data register stores the reload value for the Frequency counter. The
stored value represents the frequency of the sound (or the tone signal from the toggle
flip-flop). The register value is reloaded into the counter at Frequency counter
underflow and PWM pulse generator underflow.
The following figure shows the relationship between the tone signal and the register
value.
■ Frequency Data Register
Figure 25.2-4 shows the relationship between a tone signal and a register value.
Figure 25.2-4 Relationship between Tone Signal and Register Value
It should be noted that modifications of the register value while operation may alter the duty cycle of 50%
depending on the timing of the modification.
bit
7
6
5
Address:
D7 D6 D5 D4 D3 D2
003546
H
R/W R/W R/W R/W
Tone signal
(register value+1) x
One PWM cycle
4
3
2
1
0
SGFR
D1 D0
Initial value
X X X X X X X X
R/W
R/W
R/W R/W
One Tone Cycle
(register value+1) x
One PWM cycle
CHAPTER 25 SOUND GENERATOR
B
539
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