WM8959 datasheet(114/155 Pages) WOLFSON

114 / 155 page

WM8959

Pre-Production

PP, May 2008, Rev 3.1

114

3-WIRE / 4-WIRE SERIAL CONTROL MODES

The WM8959 is controlled by writing to registers through a 3- or 4-wire serial control interface. A

control word consists of 24 bits. The first bit is the read/write bit (R/W), which is followed by 7

address bits (A6 to A0) that determine which control register is accessed. The remaining 16 bits (B15

to B0) are data bits, corresponding to the 16 bits in each control register.

The 3- or 4-wire modes are selected by the RD_3W_ENA register bit. Additionally the MODE_3W4W

control bit can be used to select between push 0/1 and open-drain or wired-OR modes, as described

in Table 69 below.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

RD_3W_ENA

3- / 4-wire readback configuration

1 = 3-wire mode

0 = 4-wire mode, using GPIO pin

R22 (16h)

MODE_3W4W

3-wire mode

0 = push 0/1

1 = open-drain

4-wire mode

0 = push 0/1

1 = wired-OR

Table 69 3-Wire / 4-Wire Control Interface Selection

3-wire control mode is selected by setting RD_3W_ENA = 1. In 3-wire mode, every rising edge of

SCLK clocks in one data bit from the SDIN pin. A rising edge on CSB/ADDR latches in a complete

control word consisting of the last 24 bits.

In Write operations (R/W=0), all SDIN bits are driven by the controlling device.

In Read operations (R/W=1), the SDIN pin is driven by the controlling device to clock in the register

address, after which the WM8959 drives the SDIN pin to output the applicable data bits.

The 3-wire control mode timing is illustrated in Figure 83.

Figure 83 3-Wire Serial Control Interface

4-wire control mode is selected by setting RD_3W_ENA = 0.

In Write operations (R/W=0), this mode is the same as 3-wire mode described above.

In Read operations (R/W=1), a GPIO pin must be selected to output SDOUT by setting

GPIOn_SEL=0110b (n= 1, 3, 4 or 5). In this mode, the SDIN pin is ignored following receipt of the

valid register address. SDOUT is driven by the WM8959.

In 4-wire Push 0/1 mode, SDOUT is driven low when not outputting register data bits. In Wired-OR

mode, SDOUT is undriven when not outputting register data bits.

The 4-wire control mode timing is illustrated in Figure 84 and Figure 85.

WM8959 Datasheet(PDF) 114 Page - Wolfson Microelectronics plc

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