Datasheet

Datasheet
BMM150 Geomagnetic Sensor
Page 34
BST-BMM150-DS001-01 | Revision 1.0 | April 2013 Bosch Sensortec
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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: