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The maximum and minimum values of the buzzer output frequency are as follows.
SGCL2
0
0
0
0
1
1
1
1
The sound generator output frequency f
(SGCL0 – SGCL1 – 2 × SGCL2 – 7)
f
= 2
SG
Substitute set 0 or 1 to SGCL0 to SGCL2 in the above expression. Substitute a decimal value to SGBR.
Where f
= 8 MHz, SGCL0 to SGCL2 is (1, 0, 0), and SGBR0 to SGBR3 is (1, 1, 1, 1), SGBR = 15.
X
Therefore,
(1 – 0 – 2 × 0 – 7)
f
= 2
SG
= 3.906 kHz
(2) Sound generator buzzer control register (SGBR)
SGBR is a register that sets the basic frequency of the sound generator output signal.
SGBR is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears SGBR to 00H.
Figure 17-4 shows the SGBR format.
CHAPTER 17 SOUND GENERATOR
SGCL1
SGCL0
f
SG2
6
0
0
f
/2
SG1
5
0
1
f
/2
SG1
7
1
0
f
/2
SG1
6
1
1
f
/2
SG1
8
0
0
f
/2
SG1
7
0
1
f
/2
SG1
9
1
0
f
/2
SG1
8
1
1
f
/2
SG1
can be calculated by the following expression.
SG
× {f
/(SGBR + 17)}
X
× {f
/(15 + 17)}
X
Maximum and Minimum Values of Buzzer Output
f
= 8 MHz
X
Max. (kHz)
Min. (kHz)
3.677
1.953
7.354
3.906
1.838
0.976
3.677
1.953
0.919
0.488
1.838
0.976
0.460
0.244
0.919
0.488
f
= 8.38 MHz
X
Max. (kHz)
Min. (kHz)
3.851
2.046
7.702
4.092
1.926
1.024
0.481
2.046
0.963
0.512
1.926
1.024
0.481
0.256
0.963
0.512
209
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