HT818D0 datasheet(5/14 Pages) HOLTEK

5 / 14 page

HT818D0

March 15, 2000

Functional Description

The HT818D0 is a mask ROM type voice synthe-

sizer with 22.4-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 22.4-second voice capacity can be divided

into sections of arbitrary length. Notice that the

silence length and end-pulse width are not in-

cluded in the memory.

By using Holtek¢s programming tools, the con-

tents and arrangement of sections, as well as

key features and FLAG output are all program-

mable before device fabrication.

The IC provides 12 key inputs (KEY1~KEY12).

Of the 12 keys, KEY1 can be optioned as a di-

rect, sequential or random trigger key. KEY12

can be selected as a stop or direct key. The re-

maining 10 keys (KEY2~KEY11) are used as di-

rect keys exclusively.

Play function block diagram

System oscillator

The HT818D0 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

530kW. The required oscillator frequency may

vary with different sampling rates in the pro-

cess of voice programming. As a result, the

value of the oscillator resistor may be differ-

ent 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.

Voice ROM

The voice ROM is originally designed to continu-

ously record the 22.4-second voice data at a 6kHz

sampling rate. A higher sampling rate can 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 re-

cording time but sacrifice voice quality.

The playback time can be significantly extended

by making use of coding efficiency, silence play-

ing, 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

composed of a voice or an interval of silence.

However, the silence length is not counted in

the voice ROM. The total number of sections in-

cluded should be less than 508 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.

The following are examples of section division:

Ke y

t ri g ger

Ke y

f eat ures

opt i o n

Ke y

fu n c ti o n

ta b l e

RO M

Vo i c e

RO M

D/ A

P l ay i ng c ont rol l og i c

Fl a g

out put

V DD

OS C 1

OS C 2

H T 818D 0

R OS C

se c. 2

s e c . N

se c. 1

s e c . 2

se c. 3

se c. 1

RO M

E x am pl e 1: O ne s e c t i o n o n l y

E x am pl e 2: 3 s ec t i on di v i s i on

E x am pl e 3: N s ec t i on d i v i s i o n

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