In the Programming Guide for this part, I noticed a mistake in Table 3-7. The 'Register Value' column should be labeled as binary instead of hex - the values themselves are already binary but with a misleading '0x' prefix. This would make the write mask make sense and explain the behavior I'm seeing on the device. (FWIW, on the device, I'm reading a reset value of 0x03 or 0b11 from this register). Please let me know if I'm misunderstanding this table.