UPD780828A Datasheet, PDF (329/472 Pages) NEC – 8-bit Single-Chip Microcontroller

Chapter 18 Sound Generator
18.1 Sound Generator Function
The sound generator has the function to operate an external speaker. The following two signals are
supplied by the sound generator.
(1) Basic cycle output signal (with/without amplitude)
A buzzer signal with a variable frequency in a range of 0.5 to 3.8 KHz (at f_X = 8.38 MHz) can be
created. 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 achieve control of the volume.
(2) Amplitude output signal
A PWM signal with a 7-bit resolution for variable amplitude can be generated independently.
Figure 19-1 shows the sound generator block diagram and Figure 19-2 shows the concept of each sig-
nal.
Figure 18-1: Sound Generator Block Diagram
SGCL0
f_X
1/2
fSG1
Inter nal bus
Sound generator control register (SGCR)
TCE SGOB SGCL2 SGCL1 SGCL0
2
fSG2
5-bit counter
Clear
Comparator
1/2
PWM amplitude
S
Q
Comparator R
4
SGOB
7
SGBR3 SGBR2 SGBR1 SGBR0
Sound generator
buzzer control
register (SGBR)
SGAM6 SGAM5 SGAM4 SGAM3 SGAM2 SGAM1 SGAM0
Sound generator
amplitude register
(SGAM)
Internal bus
SGO/
SGOF/
P60
PCL/
SGOA/
P61
P61 output
latch
Clock output
control circuit (PCL)
PM61
Port mode
register 6
(PM6)
User’s Manual U16504EE1V1UD00
329