HT36B2 datasheet(17/39 Pages) HOLTEK

17 / 39 page

HT36B2

Rev. 1.10

March 10, 2005

· CH3~0 channel number selection

The HT36B2 has a built-in 16 output channels and

CH3~0 is used to define which channel is selected.

When this register is written to, the wavetable synthe-

sizer will automatically output the dedicated PCM

code. So this register is also used as a start playing

key and it has to be written to after all the other

wavetable function registers are already defined.

· Change parameter selection

These two bits, VM and FR, are used to define which

There are two modes that can be selected to reduce

the process of setting the register. Refer to the follow-

ing table:

Function

Update all the parameter

Only update the frequency number

Only update the volume

· Output frequency definition

The data on BL3~0 and FR11~0 are used to define

the output speed of the PCM file, i.e. it can be used to

generate the tone scale. When the FR11~0 is 800H

and BL3~0 is 6H, each sample data of the PCM code

will be sent out sequentially.

When the fOSC is 12.8MHz, the formula of a tone fre-

quency is:

fOUT=fRECORD

50kHz

FR11 ~ 0

(17 BL3~0)

where fOUT is the output signal frequency, fRECORD and

SR is the frequency and sampling rate on the sample

code, respectively.

So if a voice code of C3 has been recorded which has

the fRECORD of 261Hz and the SR of 11025Hz, the tone

frequency (fOUT) of G3: fOUT=196Hz.

Can be obtained by using the formula:

196Hz= 261Hz

50kHz

11025Hz

FR11 ~ 0

(17 BL3~0)

A pair of the values FR11~0 and BL3~0 can be deter-

mined when the fOSC is 12.8MHz.

· Start address definition

The HT36B2 provides two address types for extended

use, one is the program ROM address which is pro-

gram counter corresponding with PF value, the other

is the start address of the PCM code.

The ST15~0 is used to define the start address of

each PCM code and reads the waveform data from

this location. The HT36B2 provides 16 input data lines

from WA15~0, the ST15~0 is used to locate the major

16 bits i.e. WA15~5 and the undefined data from

WA4~0 is always set as 00000b. In other words, the

WA15~0=ST15~0

´25. So each PCM code has to be

located at a multiple of 32. Otherwise, the PCM code

will not be read out correctly because it has a wrong

start code.

· Waveform format definition

The HT36B2 accepts two waveform formats to ensure

a more economical data space. WBS is used to define

the sample format of each PCM code.

¨ WBS=0 means the sample format is 8-bit

¨ WBS=1 means the sample format is 12-bit

The 12-bit sample format allocates location to each

sample data. Refer to the waveform format statement

as shown below.

· Repeat number definition

The repeat number is used to define the address

which is the repeat point of the sample. When the re-

peat number is defined, it will be output from the start

code to the end code once and always output the

range between the repeat address to the end code

(80H) until the volume becomes close.

The RE14~0 is used to calculate the repeat address

of the PCM code. The process for setting the RE14~0

is to write the 2

¢s complement of the repeat length to

RE14~0, with the highest carry ignored. The HT36B2

will retrieve the repeat address by adding the RE14~0

to the address of the end code, then jump to the ad-

dress to repeat this range.

· Left and Right volume control

The HT36B2 provides the left and right volume control

independently. The left and right volume are con-

trolled by VL9~0 and VR9~0 respectively. The chip

provides 1024 levels of controllable volume, the 000H

is the maximum and 3FFH is the minimum output vol-

ume.

· Envelope type definition

The HT36B2 provides a function to easily program the

envelope by setting the data of ENV1~0 and A_R. It

forms a vibrato effect by a change of the volume to at-

tach and release alternately.

The A_R signal is used to define the volume change in

attach mode or release mode and ENV1~0 is used to

define which volume control bit will be changeable.

On the attach mode, the control bits will be sequen-

tially signaled down to

²0². On the release mode, the

control bits will be sequentially signaled up to

²1². The

relationship is shown in the following table.

1 B

2 B

3 B

4 B

5 B

6 B

7 B

8 B

1 H

1 M

1 L

2 L

2 H

2 M

3 H

3 M

A s a m p l i n g d a t a c o d e ; B m e a n s o n e d a t a b y t e .

8 - B i t

1 2 - B i t

3 L

N o t e : " 1 H " H i g h N i b b l e

" 1 M " M i d d l e N i b b l e

" 1 L " L o w N i b b l e

A s a m p l i n g d a t a c o d e

Waveform Format

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