HT819D0 datasheet(4/13 Pages) HOLTEK

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Functional Description

The HT819D0 is a mask ROM type voice synthe-

sizer with 4.2-second voice capacity. A group of

pre-recorded voice sections is played upon receipt

of key trigger input signals. Two FLAG signals are

output while playing voices.

The 4.2-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, as well

as key features and FLAG output are all pro-

grammable before device fabrication.

The IC provides 6 key inputs (KEY1~KEY6). Of

the 6 keys, KEY1 can be optioned as a direct,

sequential or random trigger key. KEY6 can be

selected as a stop or direct key. The remaining

5 keys (KEY2~KEY6), are used as direct keys

exclusively.

System oscillator

The HT819D0 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, it is immediately 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 4.2-second voice data at a 6kHz

sampling rate. A higher sampling rate will gener-

ate voices of better playback quality, but will

shorten the total recording time. On the other

hand, a lower sampling rate results 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 voice ROM. During programming,

the customer’s voice sources can be divided into

as many sections as required. A section can be

comprised by a voice or an interval of silence.

However, the silent length is not counted in

voice ROM. The total number of sections in-

cluded should be less than 252 due to the space

limitation of the function table ROM. The total

length of the included sections is limited 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.

HT819D0

6th May ’98

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