CS4215 datasheet(22/52 Pages) CIRRUS

22 / 52 page

of 128 (80 Hex) is considered analog zero for

the 8-bit unsigned format.

A non-linear coding scheme is used for the com-

panded formats as shown in Figure 14. This

scheme is compatible with CCITT G.711. Com-

panding uses more precision at lower amplitudes

at the expense of less precision at higher ampli-

tudes.

µ-Law is equivalent to 13 bits at low

signal levels and A-Law is equivalent to 12 bits.

This low-level dynamic range is obtained at the

expense of large-signal dynamic range which, for

both

µ-Law and A-Law, is equivalent to 6 bits.

The CS4215 internally operates at 16 bits. The

companded data is expanded to the upper 13

(12) bits for the DACs and compressed from the

upper 13 (12) bits to 8 bits for the ADCs.

Data Time Slot 1&2, Left Channel Audio Data

Time slot 1 and 2 contain audio data for the left

channel. In mono modes, only the left channel

data is used, however both the right and left

output DACs are driven. In 8-bit modes, only

time slot 1 is used for the data.

Data Time Slot 3&4, Right Channel Audio Data

Time slot 3 and 4 contains audio data for the

right channel. In mono modes, the right ADC

outputs zero and the right DAC uses the left

digital data. In 8-bit modes, only time slot 3 is

used for the data.

Figure 15 summarizes all the time slot bit alloca-

tions for the 4 data modes and for control mode.

Reset

RESET going low causes all the internal control

registers to be set to the states shown with each

and high at least once after power up. RESET

returning high causes the CS4215 to execute an

offset calibration cycle. RESET or D/C returning

high should occur at least 50 ms after the power

supply has stabilized to allow the voltage refer-

ence to settle.

Data Time Slot 5, Output Setting

LO5

LO4

LO3

LO2

LO1

LO0

00111111

Reset (R)

BIT

NAME

VALUE

FUNCTION

LO5-0

Left Channel Output

Attenuation Setting

1 1 1 1 1 1

R 1.5dB attenuation steps. LO5 is the MSB.

0 = no attenuation. 111111 = -94.5dB

Line Output Enable

R Analog line outputs off (muted).

Analog line outputs on.

Headphone Output

Enable

R Headphone output off (muted).

Headphone output on.

+FS

-FS

DIGITAL CODE

A-Law: 2Ah

15h

95h

AAh

7Fh/FFh

55h/D5h

00h

3Fh

BFh

80h

u-Law:

Figure 14. Companded Data Formats

CS4215

DS76F2

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