WM9090ECSSLASHR datasheet(34/81 Pages) WOLFSON

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WM9090

Production Data

PD, November 2010, Rev 4.1

CONTROL INTERFACE

The WM9090 is controlled by writing to registers through a 2-wire serial control interface. Readback

is available for all registers, including Chip ID and power management status.

The WM9090 is a slave device on the control interface; SCLK is a clock input, while SDA is a bi-

directional data pin. To allow arbitration of multiple slaves (and/or multiple masters) on the same

interface, the WM9090 transmits logic 1 by tri-stating the SDA pin, rather than pulling it high. An

external pull-up resistor is required to pull the SDA line high so that the logic 1 can be recognised by

the master. Note that the control interface can support I/O levels up to 2.7V.

In order to allow many devices to share a single 2-wire control bus, every device on the bus has a

unique 8-bit device ID (this is not the same as the 8-bit address of each register in the WM9090).

The WM9090 device ID is 1101_1100 (DCh). The LSB of the device ID is the Read/Write bit; this bit

is set to logic 1 for “Read” and logic 0 for “Write”.

The WM9090 operates as a slave device only. The controller indicates the start of data transfer with

a high to low transition on SDA while SCLK remains high. This indicates that a device ID, register

address and data will follow. The WM9090 responds to the start condition and shifts in the next eight

bits on SDA (8-bit device ID including Read/Write bit, MSB first). If the device ID received matches

the device ID of the WM9090, then the WM9090 responds by pulling SDA low on the next clock

pulse (ACK). If the device ID is not recognised or the R/W bit is ‘1’ when operating in write only

mode, the WM9090 returns to the idle condition and waits for a new start condition and valid

address.

If the device ID matches the device ID of the WM9090, the data transfer continues as described

below. The controller indicates the end of data transfer with a low to high transition on SDA while

SCLK remains high. After receiving a complete address and data sequence the WM9090 returns to

the idle state and waits for another start condition. If a start or stop condition is detected out of

sequence at any point during data transfer (i.e. SDA changes while SCLK is high), the device returns

to the idle condition.

The WM9090 supports the following read and write operations:



Single write



Single read



Multiple write using auto-increment



Multiple read using auto-increment

WM9090ECS/R Datasheet(PDF) 34 Page - Wolfson Microelectronics plc