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EPSON
S1C88409 TECHNICAL MANUAL
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Sound Generator)
DUTY0–DUTY2: Duty ratio selection register (00FF55HD4–D6)
Selects the duty ratio of the BZ signal.
Table 5.15.6.3 Duty ratio settings
Level
Level 1 (Max)
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8 (Min)
12/28
11/28
10/28
9/28
8/28
7/28
6/28
5/28
4096.0
2048.0
3276.8
1638.4
2730.7
1365.3
2340.6
1170.3
DUTY0
DUTY2
DUTY1
8/20
7/20
6/20
5/20
4/20
3/20
2/20
1/20
0
1
0
1
0
1
0
1
0
1
8/16
7/16
6/16
5/16
4/16
3/16
2/16
1/16
12/24
11/24
10/24
9/24
8/24
7/24
6/24
5/24
0
1
0
1
Duty ratio by buzzer frequencies (Hz)
The buzzer sound level can be adjusted by selecting the duty ratio from among the above 8
types. However, when the envelope has been set to ON (ENON = "1"), this setting becomes
invalid.
At initial reset, the DUTY register is set to "0" (level 1).
ENRST: Envelope reset (00FF54HD2)
Resets the envelope.
When "1" is written: Reset
When "0" is written: No operation
Reading: Always "0"
The envelope is reset by writing "1" to ENRST and
the duty ratio returns to level 1 (maximum).
Writing "0" to ENRST and writing "1" when an
envelope has not been added become invalid.
Since ENRST is exclusively for writing, it always
becomes "0" during reading.
ENON: Envelope ON/OFF control register
(00FF54HD1)
Controls the addition of an envelope to the BZ
signal.
When "1" is written: ON
When "0" is written: OFF
Reading: Valid
By writing "1" to ENON, an envelope can be added
to BZ signal output. When "0" is written, an
envelope is not added and the BZ signal is fixed at
the duty ratio selected in DUTY0–DUTY2.
At initial reset and when "1" is written to BZSHT,
the ENON register is set to "0" (OFF).
ENRTM: Envelope attenuation time selection
register (00FF54HD3)
Selects the envelope attenuation time that is added
to the BZ 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 attenuation time of the digital envelope is
determined by the time for changing the duty
ratio.
The duty ratio is changed in 125 msec (8 Hz) units
when "1" is written to ENRTM and in 62.5 msec
(16 Hz) units, when "0" is written.
This setting becomes invalid when an envelope
has been set to OFF (ENON = "0").
At initial reset, the ENRTM register is set to "0" (0.5
sec).
SHTPW: One-shot buzzer output duration width
selection register (00FF54HD4)
Selects the output duration width of the one-shot
buzzer.
When "1" is written: 125 msec
When "0" is written: 31.25 msec
Reading: Valid
The one-shot buzzer output duration width is set
to 125 msec when "1" is written to SHTPW and
31.25 msec, when "0" is written.
At initial reset, the SHTPW register is set to "0"
(31.25 msec).