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4.12.3 Control of buzzer output
The BZ signal generated by the sound generator is output from the BZ terminal by setting "1" for the
buzzer output enable register BZE. When "0" is set to BZE register, the output terminal shifts to the low
(V
) level (negative polarity) or high (V
SS
Note: Since it generates a BZ signal that is out of synchronization with the BZE register, hazards may at
times be produced when the signal goes ON/OFF due to the setting of the BZE register.
4.12.4 Setting of buzzer frequency and sound level
The divided signal of the OSC1 oscillation clock (32.768 kHz) is used for the buzzer (BZ) signal and it is
set up such that 8 types of frequencies can be selected by changing this division ratio. Frequency selection
is done by setting the buzzer frequency selection registers BZFQ0–BZFQ2 as shown in Table 4.12.4.1.
The buzzer sound level is changed by controlling the duty ratio of the buzzer signal.
The duty ratio can be selected from among the 8 types shown in Table 4.12.4.2 according to the setting of
the buzzer duty selection registers BDTY0–BDTY2.
Level
Level 1 (Max.)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8 (Min.)
When the HIGH level output time has been made TH and when the LOW level output time has been made
TL due to the ratio of the pulse width to the pulse synchronization, the duty ratio becomes TL/(TH+TL)
for negative polarity or TH/(TH+TL) for positive polarity.
When BDTY0–BDTY2 have all been set to "0", the duty ratio becomes maximum and the sound level also
becomes maximum. Conversely, when BDTY0–BDTY2 have all been set to "1", the duty ratio becomes
minimum and the sound level also becomes minimum.
The duty ratio that can be set is different depending on the frequency that has been set, so see Table 4.12.4.2.
S1C63454 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Sound Generator)
) level (positive polarity).
DD
BZE register
"0"
BZ output/BZ terminal
(Negative polarity)
BZ output/BZ terminal
(Positive polarity)
Fig. 4.12.3.1 Buzzer signal output timing chart
Table 4.12.4.1 Buzzer signal frequency setting
BZFQ2
BZFQ1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
Table 4.12.4.2 Duty ratio setting
BDTY2
BDTY1
BDTY0
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
"1"
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
Duty ratio by buzzer frequency (Hz)
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
EPSON
"0"
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
79
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