I recently observed something unusual on an ADIS16365. When the master system read the MSC_CTRL register, several of the bits that are marked as "not used" in the ICD (datasheet) returned "1". Specifically it should have read 0x84, but it returned 0xB084. This means that bits 12:15 which are listed as "not used" returned "1011" (MSB first). This ended up throwing a BIT (built-in-test) failure at master system level because it did not match the expected value.
Is this normal? Are these bits used for some "secret" test function that is not documented? If so, can you tell me what this means? Did the IMU experience an internal fault of some kind?
Thanks for you help!