Digital Envelope; One-Shot Output - Epson 0C88832 Technical Manual

5.12.4 Digital envelope

A digital envelope with duty control can be added
to the buzzer signal.
The envelope can be realized by staged changing of
the same duty ratio as detailed in Table 5.12.3.2 in
the preceding section from level 1 (maximum) to
level 8 (minimum).
The addition of an envelope to the buzzer signal
can be done by writing "1" to the envelope control
register ENON. When "0" is written, the duty ratio
is set at the level selected in DUTY0–DUTY2.
BZFQ0–2
ENON
ENRST
ENRTM
BZON
Buzzer
level 1 (MAX)
signal
duty ratio

5.12.5 One-shot output

The sound generator has a built-in 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 the
one-shot buzzer duration selection register SHTPW
for buzzer signal output time.
The output control of the one-shot buzzer is done
by writing "1" to the one-shot buzzer trigger
BZSHT, then the buzzer signal is output in synchro-
nization with the internal 256 Hz signal from the
output port terminal. Thereafter, when the set time
has elapsed, the buzzer signal in synchronization
with the 256 Hz signal automatically goes OFF in
the same manner.
The BZSHT can be read to determine status. When
BZSHT is "1", it indicates a BUSY status (during
one-shot output) and when BZSHT is "0", it indi-
cates a READY status (during stop).
When you want to turn the buzzer signal OFF prior
to the elapse of the set time, the buzzer signal can
be immediately stopped (goes OFF in
asynchonization with 256 Hz signal) by writing "1"
to the one-shot forced stop bit BZSTP.
E0C88832/88862 TECHNICAL MANUAL
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (Sound Generator)
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
Fig. 5.12.4.1 Timing chart of digital envelope
By writing "1" to ENON to turn the buzzer output
ON (writing "1" to BZON), the buzzer signal with a
level 1 duty ratio is output, and then the duty ratio
can be attenuated in stages to level 8. The attenu-
ated envelope can be returned to level 1 by writing
"1" to the envelope reset bit ENRST. When attenu-
ated to level 8, the duty level remains at level 8
until the buzzer output is turned OFF (writing "0"
to BZON) or writing "1" to ENRST.
The stage changing time for the envelope level can
be selected either 125 msec or 62.5 msec by the
envelope attenuation time selection register
ENRTM.
Figure 5.12.4.1 shows the timing chart of the digital
envelope.
No change of duty level
t
11
01
t
12
t
13
t
14
t
t = 125
11
t = 125 msec
12–17
Since the one-shot output has a short duration, an
envelope cannot be added. (When "1" is written to
BZSHT, ENON is automatically reset to "0".)
Consequently, only the frequency and sound level
can be set for one-shot output.
The control for the one-shot output is invalid
during normal buzzer output.
Figure 5.12.5.1 shows the timing chart of the one-
shot output.
256 Hz
SHTPW
BZSHT(W)
BZSHT(R)
BZSTP
BZ output (R50)
BZ output (R51) *
Fig. 5.12.5.1 Timing chart of one-shot output
EPSON
15
t
16
t
17
+0
msec
–4
∗ when selected by mask option
105