
I-96
EPSON
S1C62N82 TECHNICAL HARDWARE
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Melody Generator)
Envelope function
The S1C62N82 Series may be added with envelope function
for melody playing by mask option. The IC internal circuit
when the envelope function is valid (when normal HIGH
level output is selected) and the external circuit required is
shown in Figure 4.11.15. The IC internal setting is done by
mask option and the following need to be externally in-
stalled:
-
piezo buzzer sounding body;
-
booster coil for raising the sound pressure of the playing;
-
PNP bipolar transistor to drive the sounding body (piezo
buzzer);
-
capacitor for implementing smooth sound pressure
attenuation; and
-
resistor for controlling the power current discharge of the
capacitor.
The output waveform when envelope function is shown in
Figure 4.11.16. The attack signal indicated in the diagram
will go high ("H" level) when the playing of the word starts if
the attack data written on the melody ROM were "1". The
pulse width is approximately 12 ms. The ATK (attack) signal
recharges the externally installed capacitor and the R12
terminal output level will be recharged up to the power
voltage as shown in Figure 4.11.16. This will result in the
MO terminal output amplitude becoming the power voltage
since they (R12 and MO terminals) are wired together inside
the IC as shown in Figure 4.11.15. The sound pressure of
the melody played then will be maximum. Henceforth,
because the capacitor connected to the R12 terminal is
discharged as the base current of the externally installed
transistor as time passes, the base current will drop and the
playing sound pressure will attenuate with the passing of
time. The MO terminal output waveform is shown in Figure
4.11.16. The MO terminal output amplitude will decrease
with capacitor discharge. This is the principle of the enve-
lope function.
Furthermore, normal LOW level output may also be se-
lected, in which case NPN transistor is used. The output
waveform in Figure 4.11.16 will also be reversed.