LSM303DLHC datasheet(21/42 Pages) STMICROELECTRONICS

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LSM303DLHC

Digital interfaces

Doc ID 018771 Rev 1

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5.1.3

Magnetic field digital interface

For magnetic sensors the default (factory) 7-bit slave address is 0011110xb.

The slave address is completed with a Read/Write bit. If the bit is ‘1’ (read), a repeated

START (SR) condition must be issued after the two sub-address bytes; if the bit is ‘0’ (write)

the master transmits to the slave with the direction unchanged.

Table 16 explains how the

SAD is composed.

Magnetic signal interface reading/writing

The interface uses an address pointer to indicate which register location is to be read from

or written to. These pointer locations are sent from the master to this slave device and

succeed the 7-bit address plus 1 bit Read/Write identifier.

To minimize the communication between the master and magnetic digital interface of

LSM303DLHC, the address pointer updates automatically without master intervention.

This automatic address pointer update has two additional features. First, when address 12

or higher is accessed, the pointer updates to address 00, and secondly, when address 08 is

reached, the pointer rolls back to address 03. Logically, the address pointer operation

functions as shown below.

If (address pointer = 08) then the address pointer = 03

Or else, if (address pointer >= 12) then the address pointer = 0

Or else, (address pointer) = (address pointer) + 1

The address pointer value itself cannot be read via the I2C bus.

Any attempt to read an invalid address location returns 0, and any write to an invalid

address location, or an undefined bit within a valid address location, is ignored by this

device.

Table 16.

SAD

Command

SAD[6:0]

R/W

SAD+R/W

Read

0011110

00111101 (3Dh)

Write

0011110

00111100 (3Ch)

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