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MP3 Audio Decoder

PT8401

PT8401 v 1.3

Page 11

Updated March 2002

Princeton Technology Corp.

Table 4. Settings for input frequency 12.288MHz.

Register Name

Value

PLLSet

0x3b28

PLLFraction

0x7e5e

The sampling frequency of ADPCM encoding is controlled by Serial Input Port 2; however, the

sampling frequency of ADPCM decoding is controlled via the setting of PLL. The microcontroller has

to be set properly to get the right listening results. The default setting for ADPCM decoding assumes

that sampling frequency is 8kHz; however, 11.025kHz and 12kHz are selectable, too.

Start-up Configuration and General Purpose IO

PT8401 offers another easy way to configure the basic start-up setting without using the external controller.

It is called “Start-up” Configuration. GPIO pins are configured as input pins before RESET. After RESET,

those values are latched to be the basic configuration of PT8401. After start-up, the GPIO pins are

configured as output pins.

START-UP CONFIGURATION

GPIO

Name

Description

0

SetMode

"0" : MPEG Mode

"1" : ADPCM Mode

1

AdpcmMode

"0" : Bitstream Decoding

"1" : Sample Encoding.

2

SP_SEL

"0" : First Serial Port

"1" : Parallel Input Port Selection (only in MPEG Decoding).

3

Set_SAO[0]

Set Serial Output Port. Same as Main Function Selection.

4

Set_SAO[1]

5

Set_SAO[2]

6

Set_SAI2[0]

Set Second Serial Input Port. Same as Main Function Selection.

7

Set_SAI2[1]