
150
EPSON
S1C88409 TECHNICAL MANUAL
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Sound Generator)
5.15 Sound Generator
5.15.1 Configuration of sound generator
The S1C88409 has a built-in sound generator for
generating BZ (buzzer) signal.
BZ signals generated from the sound generator can
be output from the R42 output port terminal.
Aside permitting the respective setting of the
buzzer signal frequency and sound level (duty
adjustment) to 8 stages, it permits the adding of a
digital envelope by means of duty ratio control. It
also has a one-shot output function for outputting
key operated sounds.
Figure 5.15.1.1 shows the configuration of the
sound generator.
Dividing circuit
256 Hz
Envelope
addition circuit
Programmable
dividing circuit
BZFQ0–BZFQ2
DUTY0–DUTY2
Duty ratio
control circuit
ENRTM
BZON
ENON
ENRST
OSC1
oscillation circuit
fOSC1
BZSHT
One-shot buzzer
control circuit
SHTPW
BZSTP
Buzzer output
control circuit
Output port
R42
BZ (R42)
Fig. 5.15.1.1 Configuration of sound generator
5.15.2 Control of buzzer output
BZ signal can be output from the R42 output port
terminal.
The configuration of the output port R42 is shown
in Figure 5.15.2.1.
The output control for the BZ signal generated by
the sound generator is done by the buzzer output
control register BZON, one-shot buzzer trigger bit
BZSHT and one-shot buzzer forced stop bit BZSTP.
When "1" is set to BZON or BZSHT, the BZ signal
is output from the R42 output port terminal and
when "0" is set to BZON or "1" is set to BZSTP, the
high (VDD) level is output. At this time, "1" must
always be set for the output data register R42D.
Figure 5.15.2.2 shows the output waveform of the
BZ signal.
Note: Since the BZ signal is generated asynchro-
nously from the registers BZON, BZSHT
and BZSTP, when the signal is turned ON
or OFF by the register settings, a hazard of
a 1/2 cycle or less is generated.
Register BZSTP
Register BZON
Register BZSHT
R
SQ
One-shot time up
R42 output
BZ signal
Register R42D
Fig. 5.15.2.1 Configuration of R42
BZON/BZSHT
BZ output (R42)
01
Fig. 5.15.2.2 Output waveform of BZ signal