User Manual

MPU-9250 Register Map and Descriptions
Document Number: RM-MPU-9250A-00
Revision: 1.4
Release Date: 9/9/2013
registers and hence the total read lengths between all the slaves cannot be greater than 24 or some
bytes will be lost.
Note: Slave 4’s behavior is distinct from that of Slaves 0-3. For further information regarding the
characteristics of Slave 4, please refer to Registers 49 to 53.
Example:
Suppose that Slave 0 is enabled with 4 bytes to be read (I2C_SLV0_EN = 1 and I2C_SLV0_LEN =
4) while Slave 1 is enabled with 2 bytes to be read, (I2C_SLV1_EN=1 and I2C_SLV1_LEN = 2). In
such a situation, EXT_SENS_DATA _00 through _03 will be associated with Slave 0, while
EXT_SENS_DATA _04 and 05 will be associated with Slave 1.
If Slave 2 is enabled as well, registers starting from EXT_SENS_DATA_06 will be allocated to Slave
2.
If Slave 2 is disabled while Slave 3 is enabled in this same situation, then registers starting from
EXT_SENS_DATA_06 will be allocated to Slave 3 instead.
Register Allocation for Dynamic Disable vs. Normal Disable
If a slave is disabled at any time, the space initially allocated to the slave in the EXT_SENS_DATA
register, will remain associated with that slave. This is to avoid dynamic adjustment of the register
allocation.
The allocation of the EXT_SENS_DATA registers is recomputed only when (1) all slaves are
disabled, or (2) the I2C_MST_RST bit is set (Register 106).
This above is also true if one of the slaves gets NACKed and stops functioning.
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