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25.2.4
Decrement Grade Register
The Decrement Grade register stores the reload value for the Decrement counter. They
are prepared to automatically decrement the stored value in the Amplitude Data
register. The register value is reloaded into the counter at Decrement counter underflow
and falling edge of tone signal.
■ Decrement Grade Register
When the DEC bit is "1" and the Decrement counter counts the number of tone pulses up to the reload
value, the stored value in the Amplitude Data register is decremented by 1(one) at the end of the tone cycle.
This operation realizes automatic de-gradation of the sound with fewer number of CPU interventions.
It should be noted that the number of the tone pulses specified by this register equals to "register value +1".
When the Decrement Grade register is set to "00
bit
7
6
5
4
Address:
D7 D6 D5 D4 D3 D2
003548
H
R/W R/W R/W R/W
3
2
1
0
SGDR
D1 D0
Initial value
X X X X X X X X
R/W
R/W
R/W R/W
", the decrement operation is performed every tone cycle.
H
CHAPTER 25 SOUND GENERATOR
B
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