EM73880 datasheet(22/40 Pages) EMC

22 / 40 page

* This specification are subject to be changed without notice.

EM73880

4-BIT MICRO-CONTROLLER FOR LCD PRODUCT

11.30.2001

Preliminary

MELODY (SOUND EFFECT) CONTROL

One channel melody/sound effect output, controlled by port 23, 24, 17, and 30.

There is a built-in sound effect. It includes the tone generator and random generator. The tone generator is a

binary down counter and the random generator is a 9-bit liner feedback shift register.

÷2

CLK/8

f2x2

P23,P24

PWM ckt.

P30

Output

control

Tone

generator

Random

generator

4 kinds

of divider

Sound effect command register (P30)

There are 4 kinds of basic frequency for sound generator which can be selected by P30. The output of sound

effect is tone and random combination.

Port30

BFREQ

SMODE

Initial value : 0000

BFREQ Basic frequency (f1) select

SMODE

Sound generator mode

CLK/4

Disable

CLK/8

Tone output

CLK/16

Random output

CLK/32

Tone+random output

(CLK=4.6MHz)

Tone frequency register (P23, P24)

The 8-bit tone frequency register is P24 and P23. The tone frequency will be changed when user output

the different data to P23. Thus, the data must be output to P24 before P23 when users want to change the

8-bit tone frequency (TF).

Port24

Port23

Initial value : 1111 1111

Higher nibble register

Lower nibble register

** f1=CLK/2X, f2=f1/(TF+1)/2, TF=1~255, TF

≠≠≠≠≠0

** Example : CLK=4.6 MHz, BFREQ=11, TF=00110001B.

⇒ f1=143.75K Hz, f2=143.75K Hz/50/2=1430 Hz

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