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BDTY0–BDTY2: Duty level selection register (FF6FH•D0–D2)
Selects the duty ratio of the buzzer signal as shown in Table 4.12.6.3.
Level
Level 1 (Max.)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8 (Min.)
The sound level of this buzzer can be set by selecting this duty ratio.
However, when the envelope has been set to on (ENON = "1"), this setting becomes invalid.
At initial reset, this register is set to "0".
ENRST: Envelope reset (FF6CH•D2)
Resets the envelope.
When "1" is written: Reset
When "0" is written: No operation
Reading: Always "0"
Writing "1" into ENRST resets envelope and the duty ratio becomes maximum. If an envelope has not
been added (ENON = "0") and if no buzzer signal is being output, the reset becomes invalid. Writing "0"
is also invalid.
This bit is dedicated for writing, and is always "0" for reading.
ENON: Envelope On/Off control register (FF6CH•D1)
Controls the addition of an envelope onto the buzzer signal.
When "1" is written: On
When "0" is written: Off
Reading: Valid
Writing "1" into the ENON causes an envelope to be added during buzzer signal output. When a "0" has
been written, an envelope is not added.
At initial reset, this register is set to "0".
ENRTM: Envelope releasing time selection register (FF6CH•D3)
Selects the envelope releasing time that is added to the buzzer signal.
When "1" is written: 1.0 sec (125 msec × 7 = 875 msec)
When "0" is written: 0.5 sec (62.5 msec × 7 = 437.5 msec)
Reading: Valid
The releasing time of the digital envelope is determined by the time for converting the duty ratio.
When "1" has been written in ENRTM, it becomes 125 msec (8 Hz) units and when "0" has been written, it
becomes 62.5 msec (16 Hz) units.
At initial reset, this register is set to "0".
S1C63656 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Sound Generator)
Table 4.12.6.3 Duty ratio setting
BDTY2
BDTY1
BDTY0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
EPSON
Duty ratio by buzzer frequency (Hz)
4096.0
3276.8
2730.7
2048.0
1638.4
1365.3
8/16
8/20
12/24
7/16
7/20
11/24
6/16
6/20
10/24
5/16
5/20
9/24
4/16
4/20
8/24
3/16
3/20
7/24
2/16
2/20
6/24
1/16
1/20
5/24
2340.6
1170.3
12/28
11/28
10/28
9/28
8/28
7/28
6/28
5/28
101
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