AD1845

–19–

REV. C

Clock and Data Format Register (IXA3:0 = 8)

IXA3:0

Data 7

Data 6

Data 5

Data 4

Data 3

Data 2

Data 1

Data 0

8

FMT1

FMT0

C/L

S/M

CFS2

CFS1

CFS0

CSS

NOTE: Placing the AD1845 in the Mode Change Enable (MCE) state is not required when changing the sample rate. However,

changes to FMT[1:0], C/L, and S/M require MCE or setting PEN = 0.

CSS

Clock Source Select. This bit in conjunction with CFS2:0 selects the audio sample rate frequency. See Figure 8

below. Note: MODE2 allows a wider range of sample rate frequencies to be selected by using the Frequency

Select Register (refer to Registers 22 and 23).

CFS2:0

Clock Frequency Divide Select. These bits in conjunction with CSS select the audio sample frequency.

CFS2

CFS1

CFS0

CSS

Sample Rate

0

0

0

0

8.0

kHz

0

0

0

1

5.5125

kHz

0

0

1

0

16.0

kHz

0

0

1

1

11.025

kHz

0

1

0

0

27.42857 kHz

0

1

0

1

18.9

kHz

0

1

1

0

32.0

kHz

0

1

1

1

22.05

kHz

1

0

0

0

Reserved

1

0

0

1

37.8

kHz

1

0

1

0

Reserved

1

0

1

1

44.1

kHz

1

1

0

0

48.0

kHz

1

1

0

1

33.075

kHz

1

1

1

0

9.6

kHz

1

1

1

1

6.615

kHz

Figure 8. MODE1 Audio Sample Frequency Select

S/M

Stereo/Mono Select. This bit determines how the audio data streams are formatted. Selecting stereo will result

with alternating samples representing left and right audio channels. Mono playback plays the same audio sample

on both channels. Mono capture only captures data from the left audio channel.

0

Mono

1

Stereo

C/L

Companded/Linear Select. This bit selects between a linear digital representation of the audio signal or a nonlinear,

companded format for all input and output data. The type of linear PCM or the type of companded format is

defined by the FMT bits.

0

Linear PCM

1

Companded

FMT[1:0]

Format Select. The bits define the format for all digital audio input and outputs based on the state of the C/L bit.

See Figure 9 for FMT and C/L bit settings that determine the audio data type format.

res

Reserved for future expansion. Always write a zero to this bit.

This register’s initial state after reset is “0000 0000.”

FMT1

FMT0

C/L

Audio Data Type

0

0

0

Linear, 8-Bit Unsigned PCM

00

1

µ-Law, 8-Bit Companded

0

1

0

Linear, 16-Bit Twos-Complement PCM Little Endian

0

1

1

A-Law, 8-Bit Companded

1

0

0

Reserved

1

0

1

Reserved

1

1

0

Linear, 16-Bit Twos Complement Big Endian

1

1

1

Reserved

Figure 9. Digital Audio Data Type