The NCT210 is a two-channel digital thermometer and over/undertemperature alarm, intended for use in personal computers and other systems requiring thermal monitoring and management. The device can measure the temperature of a microprocessor using a diode-connected PNP transistor, which can be provided on-chip with the processor, or can be a low cost discrete NPN/PNP device, such as the 2N3904/2N3906. A novel measurement technique cancels out the absolute value of the transistor's base emitter voltage so that no calibration is required. The second measurement channel measures the output of an on-chip temperature sensor to monitor the temperature of the device and its environment. The NCT210 commumicates over a two-wire serial interface compatible with SMBus standards. Under/overtemperature limits can be programmed into the device over the serial bus, and an /ALERT output signals when the on-chip or remote temperature is out of range. This output can be used as an interrupt or as an SMBus alert.