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PT2257 V1.4

- 8 -

May, 2008

Electronic Volume Controller IC

PT2257

DATA BYTES DESCRIPTION

FUNCTION BITS

MSB

2

3

4

5

6

7

LSB

Function

1

1

1

1

1

1

1

1

Function OFF (-79dB)

1

1

0

1

A3

A2

A1

A0

2-Channel, -1dB/step

1

1

1

0

0

B2

B1

B0

2-Channel, -10dB/step

1

0

1

0

A3

A2

A1

A0

Left Channel, -1dB/step

1

0

1

1

0

B2

B1

B0

Left Channel, -10dB/step

0

0

1

0

A3

A2

A1

A0

Right Channel, -1dB/step

0

0

1

1

0

B2

B1

B0

Right Channel, -10dB/step

0

1

1

1

1

0

0

M

2-Channel, MUTE

When M=1, MUTE=ON

When M=0, MUTE=OFF

ATTENUATION UNIT BIT

A3

A2/B2

A1/B1

A0/B0

Attenuation Value (dB)

0

0

0

0

0/0

0

0

0

1

-1/-10

0

0

1

0

-2/-20

0

0

1

1

-3/-30

0

1

0

0

-4/-40

0

1

0

1

-5/-50

0

1

1

0

-6/-60

0

1

1

1

-7/-70

1

0

0

0

-8/

1

0

0

1

-9/

Where: Ax=-dB/step, Bx=-10dB/step

For example, for a Left Channel Attenuation at -33dB, the data byte is as follows:

START

1

0

1

1

0

0

1

1

ACK

1

0

1

0

0

0

1

1

ACK STOP

Left Channel -30dB

Left Channel -3dB