The MC1066 is a serially programmable temperature sensor optimized for monitoring modern high performance CPUs with on-board integrated temperature sensing diodes. Temperature data is converted from the CPU's diode outputs and made available as an 8-bit digital word. Communication with the MC1066 is accomplished via the standard System Management Bus (SMBus) commonly used in modern computer systems. This permits reading the current internal/external temperature, programming the threshold setpoints, and configuring the device. Additionally, an interrupt is generated on the ALERT/COMP pin when temperature moves outside the preset threshold windows in either direction. A separate CRITICAL setpoint is provided through external hardwiring for "fail safe" operation per ACPI guidelines. A Standby command may be sent via the SMBus or by signaling the STBY input pin to activate the low-power Standby mode. Registers can be accessed while in Standby mode. Address selection inputs allow up to nine MC1066s to share the same 2-wire SMBus for multi-zone monitoring. All registers can be read by the host, and both polled and interrupt driven systems are easily accommodated. Small size, low installed cost, and ease of use make the MC1066 an ideal choice for implementing sophisticated system management schemes, such as ACPI.