The LM79 is a highly integrated Data Acquisition system for hardware monitoring of servers, Personal Computers, or virtually any microprocessor based system. In a PC, the LM79 can be used to monitor power supply voltages, temperatures, and fan speeds. Actual values for these inputs can be read at any time, and programmable WATCHDOG limits in the LM79 activate a fully programmable and maskable interrupt system with two outputs. The LM79 has an on-chip temperature sensor, 5 positive analog inputs, two inverting inputs (for monitoring negative voltages), and an 8-bit ADC. An input is provided for the overtemperature outputs of additional temperature sensors and this is linked to the interrupt system. The LM79 provides inputs for three fan tachometer outputs. Additional inputs are provided for Chassis Intrusion detection circuits, 5 VID monitor inputs, and chainable interrupt. The LM79 provides both ISA and Serial Bus interfaces. A 32-byte auto-increment RAM is provided for POST (Power On Self Test) code storage. Compared to the LM78, the LM79 has the following differences: an additional VID input pin, an additional register for device identification and open drain Power Switch Bypass Output.