The M5879 monitors 4 analog positive voltages, 2 fan speeds, and 2 thermal sensing inputs. When starting the monitor function on the chip, the watchdog machine monitors every function and stores the value to registers. If the monitor value exceeds the limit value, the interrupt status will be set to 1.
The M5879 continuously converts analog inputs to 8-bit digital words with a 16mV LSB weighting, yielding input ranges of 0V to 4.08V. Temperature is converted to an 8-bit two's complement digital word with 1C LSB. Fan inputs measure the period between tachometer pulses from the fans, providing a higher count for lower fan speeds. The fan inputs are digital inputs with an acceptable range of
0V to 5V and a transition level of approximately 1.4V. Fullscale fan counts are 255 (8-bit counter) and this represents a stopped or very slow fan. Nominal speeds, based on a count of 109, are programmable from 1100 to 8800RPM.