
152
EPSON
S1C88409 TECHNICAL MANUAL
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Sound Generator)
BZFQ0–2
ENON
ENRST
ENRTM
BZON
t01
t02
t03
t04
t05
t06
t07
t01
t11
t12
t13
t14
t15
t16
t17
level 1 (MAX)
2
3
4
5
6
7
8 (MIN)
BZ signal
duty ratio
No change of duty level
t01
t02–07
= 62.5
msec
= 62.5 msec
+0
–4
t11
t12–17
= 125
msec
= 125 msec
+0
–4
Fig. 5.15.4.1 Timing chart of digital envelope
5.15.5 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 BZ signal is output in synchroni-
zation with the internal 256 Hz signal from the R42
output port terminal. Thereafter, when the set time
has elapsed, the BZ 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
indicates a READY status (during stop).
When you want to turn the BZ signal OFF prior to
the elapse of the set time, the BZ signal can be
immediately stopped (goes OFF in
asynchonization with 256 Hz signal) by writing "1"
to the one-shot forced stop bit BZSTP.
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 5.15.5.1 shows the timing chart of the one-
shot output.
256 Hz
SHTPW
BZSHT(W)
BZSHT(R)
BZSTP
BZ output (R42)
Fig. 5.15.5.1 Timing chart of one-shot output