MAX31856 is very easy to use but the device also includes some optional registers if the engineers wants to implement some different functional modes. Over- and Under temperature Fault Detection is implemented with four registers that contain over- and under temperature thresholds for the linearized and cold-junction-compensated temperature. If a threshold is exceeded, the corresponding bit is set in the Fault Status register (0Fh) and, if not masked, the FAULT output will assert. The internal circuitry is protected from excessive voltages applied to the thermocouple cables by integrated MOSFETs at the T+ and T- inputs, and the BIAS output. These MOSFETs turn off when the input voltage is negative or greater than VDD. The MOSFETs are capable of withstanding input voltages up to ±45 V. If fault voltages beyond the ±45 V limits are expected, external protection should be added. Detection of open-circuit faults, such as those caused by broken thermocouple wires, can be enabled or disabled using bits 4 and 5 in the Configuration 0 register (00h). Fault detection is accomplished by forcing a small current through the thermocouple wires. An open circuit fault is indicated by the Open Fault bit, Bit 0, in the Fault Status register (0Fh) and the FAULT pin asserts if not masked.