4-9

D. Digital Attenuator

[Related pins] ATT, SHIFT, LATCH

The output data can be attenuated independently in the L

and R channels, using the transfer data from the external

microcomputer.

The ATT data of the L and R channels consist of eight bits

each, and the L and R channels can be attenuated com-

monly using the ATT control bit. (The L channel attenuation

value is used when the L and R channels are commonly

attenuated).

(1) Command and Audio Output

The attenuation data of the L and R channels consist of eight

bits, it can be set 255 ways. The following table shows the

relationship between the commands and the outputs.

The attenuation values for 01 (H) to FE (H) can be obtained

with the following equation:

E. Digital Attenuator

Suppose that there are attenuation data ATT1, ATT2 and

ATT3, and their relationship is ATT1>ATT3>ATT2. When

ATT2 is transferred before the level reaches the value of

ATT1 (point A in the figure), the level keeps approaching to

the value of ATT2. Next, when ATT3 is transferred before

the level reaches the value of ATT2 (point B or C in the fig-

ure), the level starts approaching to the value of ATT3 from

its level at that time (point B or C in the figure). The transition

(0 dB to

F. Output Selection

[Related pins] ATT, SHIFT, LATCH

The L and R channel outputs can be set in four combinations

[L/RL + R/Mute] (16 ways in total) using the transfer data

from the external microcomputer. The following table shows

the relationship between the commands and the outputs.

CONTROL

BIT

CONTROL

WHEN SYSTEM IS CLEARED

L7 TO L0

The L channel attenuation data.

FF (H)

R7 to R0

The R channel attenuation data.

FF (H)

P3 to P0

Output selection.

9 (H) Stereo

E

De-emphasis (High = on, Low = off)

However, the time constant of the emphasis is

γ 1 = 50µs and γ 2 = 15µs

is not 44.1kHz.

OFF

A

Attenuate (Low = independent, High = common). However, the L channel

attenuation value is used when the L and R channels are commonly atten-

uated.

Independent

XDon’t care.

NOTE: When the data is more than three bytes are transferred to the ATT pin, only the three bytes transferred finally are effective.

ATTENUATION DATA

L7 TO L0/R7 TO R0

AUDIO OUTPUT

FF (H)

0dB

FE (H)

↓

01 (H)

-0.034dB

↓

-48.131dB

00 (H)

-

∞

ATT = 20log [Input data/255] dB

Ex. for attenuating data FA (H)

ATT = 20log [250/255] db = 0.172dB

0dB

A

ATT1

B

ATT3

C

ATT2

FIGURE 7. METHOD OF OBTAINING AN ATTENUATION VALUE

HI2559, CXD2559