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CHAPTER 17 SOUND GENERATOR
17.1 Sound Generator Function
The sound generator has the function to sound the buzzer from an external speaker, and the following two signals
are output.
(1) Basic cycle output signal (with/without amplitude)
The signal is a buzzer signal with a variable frequency. By setting bits 0 to 2 (SGCL0 to SGCL2) of the sound
generator control register (SGCR), the signal in a range of 0.25 to 7.7 kHz can be output (when f
X
= 8.38 MHz).
The amplitude of the basic cycle output signal can be varied by ANDing the basic cycle output signal with the
7-bit-resolution PWM signal, to enable control of the buzzer sound volume.
(2) Amplitude output signal
A PWM signal with a 7-bit resolution for variable amplitude can be independently output.
Figure 17-1 shows the sound generator block diagram and Figure 17-2 shows the concept of each signal.
Figure 17-1. Sound Generator Block Diagram
Internal bus
Internal bus
Sound generator control register (SGCR)
TCE SGOB SGCL2 SGCL1 SGCL0
2
4
7
Q
f
X
f
SG1
f
SG2
1/2
1/2
Selector
Prescaler
Selector
Selector
5-bit counter
Comparator
Comparator
SGO/SGOF/P61
PCL/SGOA/P60
Clear
PWM amplitude
S
R
SGOB
SGCL0
SGBR3 SGBR2 SGBR1 SGBR0
SGAM6 SGAM5 SGAM4 SGAM3 SGAM2 SGAM1 SGAM0
P60 output
latch
Clock output
control circuit (PCL)
PM60
Sound generator buzzer
control register (SGBR)
Sound generator amplitude
register (SGAM)
Port mode
register 6 (PM6)
Summary of Contents for mPD780973 Series
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