Advanced Information

WM8740

WOLFSON MICROELECTRONICS LTD

AI Rev 1.7 July 2000

9

8 X FS INPUT SAMPLE RATE

Due to the higher speed of the interface in 8 x fs mode, audio data is input on two pins. The MODE

pin (pin 24) is used as the second input for the right channel data and left data is input on DIN (pin2).

In this mode, software control of the device is not available. The data can be input in two formats, left

or right justified, selectable by ML/I2S and two word lengths (20 or 24 bit), selectable by CSBIWO. In

both modes the data is always clocked in MSB first.

For left justified data the word start is marked by the falling edge of LRCIN. The data is clocked in on

the next 20/24 BCKIN rising edges. This format is compatible with devices such as the PMD100.

For right justified the data is justified to the rising edge of LRCIN and the data is clocked in on the

preceding 20/24 BCKIN rising edges before the LRCIN rising edge. This format is compatible with

devices such as the DF1704 or SM5842.

In both modes the polarity of LRCIN can be switched using MD/DM0.

Differential hardware mode can be used in conjunction with 8fs mode by setting the DIFFHW

pin high. In differential 8fs mode the data is input on DIN and output differentially. MODE is

unused and must be tied low.

LRCIN (PIN 1)

LEFT AUDIO

DATA DIN

(PIN 2)

RIGHT AUDIO

DATA MODE

(PIN 24)

BCKIN (PIN 3)

1/8fs

B19

B22

B23

B20

B21

B2

B1

B0

B23

B22

B21

B20

B19

B22

B23

B20

B21

B2

B1

B0

B23

B22

B21

B20

LRCIN (PIN 1)

LEFT AUDIO

DATA DIN

(PIN 2)

RIGHT AUDIO

DATA MODE

(PIN 24)

BCKIN (PIN 3)

1/8fs

B19

B22

B23

B20

B21

B2

B1

B0

B19

B22

B23

B20

B21

B2

B1

B0

Figure 5 Audio Data Input Format (8 x fs Operation)

MODES OF OPERATION

Control of the various modes of operation is either by software control over the serial interface, or

by hard-wired pin control. Selection of software or hardware mode is via MODE pin. The following

functions may be controlled either via the serial control interface or by hard wiring of the

appropriate pins.

HARDWARE CONTROL MODES

When the MODE pin is held ‘low’ the following hardware modes of operation are available. In

Hardware differential mode or 8X mode some of these modes/control words are altered or

unavailable.