Start

Condition

Stop

Condition

Data

ACK

SDA

SCL

ACK

ACK

Data

ACK

P

S

6 - 0

7 - 1

0

7 - 1

0

W

Host

Address

Start

Condition

SDA

SCL

Register

Address

Stop

Condition

ENB

SCK

SDI

Register Address

Data

ENB

SCK

SDI

7

0

7

0

LM4937

SNAS369J – OCTOBER 2006 – REVISED MAY 2013

www.ti.com

SYSTEM CONTROL

with the MODE pin. This interface is used to configure the operating mode, interfaces, data converters, mixers

and amplifiers. The LM4937 is controlled by writing 8 bit data into a series of write-only registers, the device is

always a slave for both type of interfaces.

THREE WIRE, SPI INTERFACE (MODE = 1)

Three Wire Mode Write Bus Transaction

Three Wire Mode Write Bus Timing

Figure 3. Three Wire Mode Write Bus

When the part is configured as an SPI device and the enable (ENB) line is lowered the serial data on SDI is

clocked in on the rising edge of the SCK line. The protocol used is 16bit, MSB first. The upper 8 bits (15:8) are

used to select an address within the device, the lower 8 bits (7:0) contain the updated data for this register.

TWO WIRE I

Figure 4. Two Wire Mode Write Bus Transaction

Figure 5. Two Wire Mode Write Bus Timing

Figure 6. Two Wire Mode Write Bus

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