WM8804 datasheet(15/66 Pages) WOLFSON

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Production Data

WM8804

PD Rev 4.1 September 2007

3-WIRE SERIAL CONTROL MODE REGISTER READ-BACK

Not all registers can be read. Only the device ID (registers R0, R1 and R2) and the status registers

can be read. These status registers are labelled as “read only” in the Register Map section.

The read-only status registers can be read back via the SDOUT pin. The registers can be read by

one of two methods, selected by the CONT register bit and the ‘W’ control bit. The oscillator must be

powered up before 3-wire control interface read-back is possible.

When CONT =1 and ‘W’=0, a single read-only register can be read back by writing to any other

When a write to the device is performed, the device will respond by returning the status byte in the

access is shown in Figure 9.

BIT

LABEL

DEFAULT

DESCRIPTION

2:0

READMUX

[2:0]

000

Status Register Select

Determines which status register

is to be read back:

000 = Interrupt Status Register

001 = Channel Status Register 1

010 = Channel Status Register 2

011 = Channel Status Register 3

100 = Channel Status Register 4

101 = Channel Status Register 5

110 = S/PDIF Status Register

R29

SPDRX1

1Dh

CONT

Continuous Read Enable

0 = Continuous read-back mode

disabled

1 = Continuous read-back mode

enabled

Table 10 Read-Back Control Register

The SDOUT pin is tri-state unless CSB is held low; therefore CSB must be held low for the duration

of the read.

Figure 9 3-Wire Control Interface Read-Back Method 1

The second method of reading the read only status registers is If CONT=0 and ‘W’=1. Using this

method the user can read back directly from a register by reading the register address. The device

will respond with the contents of the register. The protocol for this read-back method is shown in

Figure 10.

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