HT812D0 datasheet(4/15 Pages) HOLTEK

4 / 15 page

Functional Description

The HT812D0 is a mask ROM type voice synthe-

sizer with 2.8-second voice capacity. A group of

pre-recorded voice sections is played upon receipt

of key trigger input signals. Two output FLAGs

send signals while playing voices.

The 2.8-second voice capacity can be divided into

sections of arbitrary length. Notice that the si-

lence length and end-pulse width are not in-

cluded in the memory.

By using HOLTEK’s programming tools, the

contents and arrangement of sections, key fea-

tures and FLAG output are all programmable

before device fabrication.

The IC provides four key inputs (KEY1~KEY4).

Of the four keys, KEY1 can be optioned as a

direct, sequential or random trigger key. KEY4

can be selected as a stop or direct key. The

remaining two keys (KEY2, KEY3), are used as

direct keys exclusively.

System oscillator

The HT812D0 has a built-in RC oscillator

which requires only one external resistor for

normal applications. The oscillator frequency is

typically 96kHz for an external resistor of

530k

Ω. The required oscillator frequency may

vary with different sampling rates in the proc-

ess of voice programming. As a result the value

of the oscillator resistor may be different for

different items.

The oscillator is turned on when triggered by a

key input. After playing, the oscillator is immedi-

ately turned off and the chip goes into the standby

state.

Play function block diagram

Voice ROM

The voice ROM is originally designed to continu-

ously record the 2.8-second voice data at about

6kHz sampling rate. A higher sampling rate can

generate voices of good playback quality, but will

shorten the total recording time. On the other

hand, a lower sampling rate will result in longer

recording time but sacrifice voice quality.

The playback time can be significantly extended

by making use of coding efficiency, silence playing,

section repeating, section cascade, etc.

Section

Section is the basic element constituting the

contents of the voice ROM. During program-

ming, the customer’s voice sources can be di-

vided into as many sections as required. A

section can be composed of a voice or an interval

of silence. However, the silent length is not

counted in the voice ROM. The total number of

sections included should be less than 124 due to

the space limitation of the function table ROM.

The total length of the included sections is lim-

ited by the voice ROM.

A section, when triggered by a key input, can be

played once, repeatedly or cascaded with other

sections, depending on the key function table

instructions.

HT812D0

5th May ’98

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