I have been using an ADXL346 successfully for 18 months. I talk to it via SPI at 4 Mhz. Lately, in a product variant, I am seeing all 0xFF for all the registers. One of my debug tools is reading all the registers and displaying them on my PC monitor. This does not happen often and I haven't a clue what I may be doing. Is all 0xFF a sign that the device is still sleeping when I think it should be awake?