3.3 SPI Commands
This SPI interface utilizes an 8-bit instruction (or command) register. The list of commands
available to end-user is presented in Table 3.
Measure mode (normal operation mode after power on)
Read and write temperature data register
Read status register
Reload NV data to memory output register
Activate Self test for X-channel
Activate Self test for Y-channel
Read X-channel acceleration through SPI
Read Y-channel acceleration through SPI
Measure mode (MEAS): Standard operation mode after power-up. During normal
operation, MEAS command is exit command from Self-Test.
Read and write temperature data register (RWTR): Temperature data register can be
read during normal operation without affecting the circuit operation. Temperature data
register is loaded in every 150 µs, and the load operation is disabled whenever the CSB
signal is low, hence CSB has to stay high at least 150 µs prior the RWTR command in order
to guarantee correct data. The data transfer is as presented in Figure 5 and data is
transferred MSB first. In normal operation, it doesn’t matter what data is written to
temperature data register during RWTR command and hence all zeros is recommended.
Read status register (RDSR): Read status register command provides access to the
status register. Status register format is shown in Table 4. Bold values in Definition column
are the expected values during normal operation.
Bit 3 = 0 Parity check hasn’t detected errors
Bit 3 = 1 Parity error detected
Bit 2 = 0 Analog test mode isn’t active
Bit 2 = 1 Analog test mode is active
Bit 1 = 0 Lock register is open
Bit 1 = 1 Lock register is locked
Bit 0 = 0 circuit is not in power down mode
Bit 0 = 1 circuit is in power down mode
Status register bit definitions
Reload NV data to memory output register (RLOAD): Reads NV data from EEPROM to
the memory output register.
Self test for X-channel (STX): STX command activates the circuit’s self test function for
the X-channel. Internal charge pump is activated and high voltage is applied to the X-
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