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5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Sound Generator)
5.12.3 Setting of buzzer frequency
and sound level
The buzzer signal is divided signal using the OSC1
oscillation circuit (32.768 kHz) as the clock source
and 8 frequencies can be selected. This selection is
done by the buzzer frequency selection register
BZFQ0–BZFQ2. The setting value and buzzer
frequency correspondence is shown in Table
5.12.3.1.
By selecting the duty ratio of the buzzer signal from
among 8 types, the buzzer sound level can be
adjusted. This selection is made in the duty ratio
selection register DUTY0–DUTY2. The setting value
and duty ratio correspondence is shown in Table
5.12.3.2.
Level
Level 1 (Max)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8 (Min)
Duty ratio refers to the ratio of pulse width to the
pulse cycle; given that HIGH level output time is
TH, and low level output time is TL the BZ signal
duty ratio becomes TH/(TH+TL) and the BZ signal
duty ratio becomes TL/(TH+TL).
When DUTY0–DUTY2 have all been set to "0", the
duty ratio becomes maximum and the sound level
also becomes maximum.
Level 1 (MAX)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8 (MIN)
(a) BZ signal
104
Table 5.12.3.2 Duty ratio settings
DUTY2
DUTY1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
TH
TL
Fig. 5.12.3.1 Duty ratio of buzzer signal waveform
Table 5.12.3.1 Buzzer signal frequency settings
BZFQ2
BZFQ1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
Duty ratio by buzzer frequencies (Hz)
DUTY0
4096.0
3276.8
2048.0
1638.4
0
8/16
8/20
1
7/16
7/20
0
6/16
6/20
1
5/16
5/20
0
4/16
4/20
1
3/16
3/20
0
2/16
2/20
1
1/16
1/20
Conversely, when DUTY0–DUTY2 have all been set
to "1", the duty ratio becomes minimum and the
sound level also becomes minimum.
Note that the duty ratio setting differ depending on
frequency. See Table 5.12.3.2.
Note: When using the digital envelope, the
DUTY0–DUTY2 setting becomes invalid.
Level 1 (MAX)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8 (MIN)
EPSON
BZFQ0
Buzzer frequency (Hz)
0
4096.0
1
3276.8
0
2730.7
1
2340.6
0
2048.0
1
1638.4
0
1365.3
1
1170.3
2730.7
2340.6
1365.3
1170.3
12/24
12/28
11/24
11/28
10/24
10/28
9/24
9/28
8/24
8/28
7/24
7/28
6/24
6/28
5/24
5/28
TL
TH
(b) BZ signal
E0C88832/88862 TECHNICAL MANUAL
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