ADXL180
Rev. 0 | Page 38 of 56
PHASE 4: AUTO-ZERO INITIALIZATION
If auto-zero is not enabled, upon entering Phase 4, the
ADXL180 immediately passes from Phase 4 to Phase 5.
Fast Auto-Zero Mode
If auto-zero is enabled, the fast auto-zero routine begins upon
entering Phase 4. The last offset average measurement (VSTZ2)
of Phase 3 is used as a starting value for the fast auto-zero
routine. This occurs whether internal or external self-test has
been selected. See the External Self-Test section. The auto-zero
function is described in the Auto-Zero Operation section.
The ADXL180 transmits the offset corrected sensor data every
228 μs in asynchronous mode during Phase 4. When in
synchronous mode, the ADXL180 transmits the offset corrected
sensor data after receiving a valid synchronization pulse during
Phase 4. The number of sensor values sent during Phase 4 is
65,535. Therefore, in asynchronous mode, the Phase 4 time
period is nominally 15 seconds long, during which time the
device fully responds to acceleration input.
Error Reporting
If an error is detected during Phase 4, (for example, offset out of
range, OTP parity error, and so forth), the appropriate error
code is set and the error state is entered. The error code is
transmitted until the device is reset. See Table 39 for error code
specifics. No acceleration data is transmitted when the
ADXL180 is in the error state.
PHASE 5: NORMAL OPERATION
If auto-zero is not enabled, upon entering Phase 5, the
ADXL180 transmits the measured (raw) acceleration signal
every 228 μs (in asynchronous mode) until power down. In
synchronous mode, raw data is transmitted in response to every
synchronization pulse until power down.
Slow Auto-Zero
If auto-zero is enabled, the slow auto-zero routine begins upon
entering Phase 5. The ADXL180 transmits the offset corrected
acceleration signal every 228 μs (in asynchronous mode) until
power down. In synchronous mode, offset corrected data is
transmitted in response to every synchronization pulse until
power down. The auto-zero function is described in the Auto-
Zero Operation section.
Error Reporting
Although the auto-zero routine continually corrects for offset
drift, if an error is detected during Phase 5, (for example, offset
out of range, OTP parity error, and so forth), the appropriate
error code is set and the error state is entered. The error code is
transmitted until the device is reset. See Table 39 for error code
specifics. No acceleration data is transmitted when the
ADXL180 is in the error state.
