56
EPSON
S1C60N16 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Sound Generator)
4.11.2 Frequency setting
The frequencies of the buzzer signals (BZ, BZ) are set by writing data to registers BZFQ0–BZFQ2.
Table 4.11.2.1 lists the register setting values and the frequencies that can be set.
Table 4.11.2.1 Setting of frequencies of buzzer signals
BZFQ
Buzzer frequency (Hz)
2
0
1
Demultiplier ratio
fOSC1/8
fOSC1/10
fOSC1/12
fOSC1/14
fOSC1/16
fOSC1/20
fOSC1/24
fOSC1/28
When fOSC1 = 32 kHz
4,096.0
3,276.8
2,730.7
2,340.6
2,048.0
1,638.4
1,365.3
1,170.3
1
0
1
0
1
0
1
0
1
0
1
0
1
Note: A hazard may be observed in the output waveform of the BZ and BZ signals when data of the
buzzer frequency selection registers (BZFQ0–BZFQ2) changes.
4.11.3 Digital envelope
A duty ratio control data envelope (with duty ratio change in eight stages) can be added to the buzzer
signal (BZ, BZ).
The duty ratio is the ratio of the pulse width compared with the pulse cycle. The BZ output is TH/
(TH+TL) when the high level output is TH and the low level output is TL. The BZ output (BZ inverted
output) is TL/ (TH+TL). Also, care must be taken because the duty ratio differs depending on the buzzer
frequency.
The envelope is added by writing "1" to register ENVON. If "0" is written the duty ratio is fixed to the
maximum. Also, if the envelope is added, the duty ratio is reverted to the maximum by writing "1" in
register ENVRST, and the duty ratio also becomes the maximum at the start of the buzzer signal output.
The decay time of the envelope (time for the duty ratio to change) can be selected with the register
ENVRT. This time is 62.5 msec (16 Hz) when "0" is written, and 125 msec (8 Hz) when "1" is written.
However, a maximum difference of 4 msec is taken from envelope-ON until the first change.
Table 4.11.3.1 lists the duty rates and buzzer frequencies. Figure 4.11.3.1 shows the digital envelope
timing chart.
Table 4.11.3.1 Duty rates and buzzer frequencies
Level 1 (max.)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8 (min.)
8/16
7/16
6/16
5/16
4/16
3/16
2/16
1/16
BZFQ
(register)
Duty rate
2
1
0
1
0
8/20
7/20
6/20
5/20
4/20
3/20
2/20
1/20
0
1
0
1
12/24
11/24
10/24
9/24
8/24
7/24
6/24
5/24
0
1
0
1
0
12/28
11/28
10/28
9/28
8/28
7/28
6/28
5/28
0
1