Datasheet

BMM150 Geomagnetic Sensor

Page 34

BST-BMM150-DS001-01 | Revision 1.0 | April 2013

Bosch Sensortec

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third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Note: Specifications within this document are subject to change without notice.

The SPI interface of the BMM150 is compatible with two modes, “00” and “11”. The automatic

selection between [CPOL = “0” and CPHA = “0”] and [CPOL = “1” and CPHA = “1”] is done

based on the value of SCK after a falling edge of CSB.

Two configurations of the SPI interface are supported by the BMM150: 4-wire and 3-wire. The

same protocol is used by both configurations. The device operates in 4-wire configuration by

default. It can be switched to 3-wire configuration by writing “1” to (0x4B) “SPI3en” after power

control bit was set. Pin SDI is used as the common data pin in 3-wire configuration.

For single byte read as well as write operations, 16-bit protocols are used. The BMM150 also

supports multiple-byte read operations.

In SPI 4-wire configuration CSB (chip select low active), SCK (serial clock), SDI (serial data

input), and SDO (serial data output) pins are used. The communication starts when the CSB is

pulled low by the SPI master and stops when CSB is pulled high. SCK is also controlled by SPI

master. SDI and SDO are driven at the falling edge of SCK and should be captured at the rising

edge of SCK.

The basic write operation waveform for 4-wire configuration is depicted in Figure 9. During the

entire write cycle SDO remains in high- impedance state.

CSB

SCK

SDI

R/W

AD6

AD5

AD4

AD3

AD2

AD1

AD0

DI5

DI4

DI3

DI2

DI1

DI0

DI7

DI6

SDO

tri-state

Z

Figure 9: 4-wire basic SPI write sequence (mode “11”)

The basic read operation waveform for 4-wire configuration is depicted in Figure 10: