WM8990ECS/RV Wolfson Microelectronics, WM8990ECS/RV Datasheet - Page 128

• Manufacturer Part Number: WM8990ECS/RV
• Description: Audio CODECs Stereo CODEC w.Class AB/D speaker driver
• Manufacturer: Wolfson Microelectronics

Specifications of WM8990ECS/RV

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

WM8990
w
Figure 86 3-Wire Serial Control Interface
3-WIRE / 4-WIRE SERIAL CONTROL MODES
The WM8990 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 78 below.
Table 78 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 WM8990 drives the SDIN pin to output the applicable data bits.
The 3-wire control mode timing is illustrated in Figure 86.
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 to 6). In this mode, the SDIN pin is ignored following receipt of the valid
register address. SDOUT is driven by the WM8990.
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 87 and Figure 88.
R22 (16h)
REGISTER
ADDRESS
15
14
BIT
RD_3W_ENA
MODE_3W4W
LABEL
1b
0b
DEFAULT
3- / 4-wire readback configuration
1 = 3-wire mode
0 = 4-wire mode, using GPIO pin
3-wire mode
4-wire mode
0 = push 0/1
1 = open-drain
0 = push 0/1
1 = wired-OR
DESCRIPTION
PD, March 2009, Rev 4.0
Production Data
128