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CHAPTER 25 SOUND GENERATOR
25.2.3
Amplitude Data Register
The Amplitude Data register stores the reload value for the PWM pulse generator. The
register value represents the amplitude of the sound. The register value is reloaded into
the PWM pulse generator at falling edge of tone signal.
■ Amplitude Data Register
When the DEC bit is "1" and the Decrement counter reaches its reload value, this register value is
decremented by 1(one). And when the register value reaches "00
However the sound generator continues its operation until the ST bit is cleared.
Figure 25.2-5 shows the relationship between the register value and the PWM pulse.
Figure 25.2-5 Relationship between Register Value and PWM Pulse
When the register value is set to "FF
540
15
14
13
12
bit
Address:
003547
H
D7 D6 D5 D4 D3 D2
R/W R/W R/W R/W
Register value
00
H
One input clock cycles
80
H
129 input clock cycles
FE
H
255 input clock cycles
FF
H
256 input clock cycles
", the PWM signal is always "1".
H
11
10
9
8
SGAR
D1 D0
Initial value
X X X X X X X X
R/W
R/W
R/W R/W
H
One PWM Cycle
256 input clock cycles
B
", further decrements are not performed.
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