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15.5
Digital envelope
A digital envelope for duty control can be added to the buzzer signal.
The envelope can be controlled by staged changing of the same duty envelope as detailed in Table 15.4.2 in the pre-
ceding item from level 1 (maximum) to level 8 (minimum). The addition of an envelope to the buzzer signal can be
done by writing "1" into ENON, but when "0" has been written it is not added.
When a buzzer signal output is begun (writing "1" into BZE) after setting ENON, the duty ratio shifts to level 1
(maximum) and changes in stages to level 8. When attenuated down to level 8 (minimum), it is retained at that level.
The duty ratio can be returned to maximum, by writing "1" into register ENRST during output of an envelope at-
tached buzzer signal.
The envelope attenuation time (time for changing of the duty ratio) can be selected by the register ENRTM. The time
for a 1 stage level change is 62.5 msec (16 Hz), when "0" has been written into ENRTM and 125 msec (8 Hz), when
to "1" has been written. However, there is also a max. 4 msec error from envelope ON, up to the first change.
Figure 15.5.1 shows the timing chart of the digital envelope.
BZFQ[2:0]
ENON
ENRST
ENRTM
BZE
BZ signal
Level 1 (Max.)
duty ratio
15.6
One-shot output
The sound generator has a one-shot output function for outputting a short duration buzzer signal for key operation
sounds and similar effects. Either 125 msec or 31.25 msec can be selected by SHTPW register for one-shot buzzer
signal output time.
The output of the one-shot buzzer is controlled by writing "1" into the one-shot buzzer trigger BZSHT. When this
trigger has been assigned, a buzzer signal in synchronization with the internal 256 Hz signal is output from the buzzer
output terminal. Thereafter, when the set time has elapsed, a buzzer signal in synchronization with the 256 Hz signal
goes off in the same manner as for the start of output.
The BZSHT also permits reading. When BZSHT is "1," the one-shot output circuit is in operation (during one-shot
output) and when it is "0," it shows that the circuit is in the ready to output status.
In addition, it can also terminate one-shot output prior to the elapsing of the set time. This is done by writing a "1"
into the one-shot buzzer stop BZSTP. In this case as well, the buzzer signal goes off in synchronization with the 256
Hz signal.
When "1" is written to BZSHT again during a one-shot output, a new one-shot output for 125 msec or 31.25 msec
starts from that point (in synchronization with the 256 Hz signal).
The one-shot output cannot add an envelope for short durations. However, the sound level can be set by selecting the
duty ratio, and the frequency can also be set.
One-shot output is invalid during normal buzzer output (during BZE = "1").
Figure 15.6.1 shows timing chart for one-shot output.
S1C63003/004/008/016 TeChniCal Manual
(Rev. 1.1)
2
t
t
01
3
t
02
4
t
03
5
t
04
6
t
05
7
t
06
8 (Min.)
t
07
+0
t
= 62.5
msec
01
–4
t
= 62.5 msec
02–07
Figure 15.
5.1 Timing chart for digital envelope
Seiko epson Corporation
No change of duty level
t
11
01
t
12
t
13
t
14
t
15
t
= 125
11
t
= 125 msec
12–17
15 SOunD GeneRaTOR
t
16
t
17
+0
msec
–4
15-3
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