LSM303DLM Datasheet, PDF (20/38 Pages) STMicroelectronics – Sensor module:3-axis accelerometer and 3-axis magnetometer

Digital interfaces
LSM303DLM
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 communication between the master and magnetic digital interface of
LSM303DLM, 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.
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Doc ID 018725 Rev 1