Oscillator failure detection circuit

An apparatus for operating a clocked electronic system using an oscillator failure detection circuit (OFDC), the apparatus comprising:

• an integrated circuit (IC) including the OFDC and further including a reference clock input configured to receive an oscillator output signal from a multiplexer (MUX) output;
• the MUX including:
• a first input, electrically coupled to an output of a primary oscillator;
• a second input, electrically coupled to an output of a secondary oscillator;
• a select input, electrically connected to a select output of a service processor;
• and
• an output, electrically connected to the reference clock input of the IC, the MUX configured to provide, based upon a logical value of a signal received at the select input, a connection from an output of one of the primary oscillator and of the secondary oscillator to the reference clock input of the IC;
• the OFDC including:
• a reference clock input electrically connected to the reference clock input of the IC;
• the RFO electrically connected to the service processor, the OFDC configured to indicate, in response to monitoring the clock input, an oscillator failure on the RFO;
• wherein the service processor configured to, in response to receiving on the RFO, an indication of an oscillator failure, drive the select input of the MUX to select an input electrically connected to the output of the secondary oscillator;
• and
• wherein the OFDC is configured to detect, independent of control signals received from other circuitry, a steady-state voltage on an oscillator output, the OFDC further configured to, in response to detecting the steady-state voltage, output an oscillator failure signal on a reference fail output (RFO).

A method for operating a clocked electronic system using an oscillator failure detection circuit (OFDC), the method comprising:

• selecting, with a service processor, a primary oscillator as an operating oscillator for the electronic system;
• clocking, with the primary oscillator, the electronic system;
• monitoring, with the OFDC, the operating oscillator for a failure condition;
• detecting, with the OFDC, the failure condition;
• sending, with the OFDC, to the service processor, an RFO signal;
• selecting, with the service processor, in response to receiving an RFO signal from the OFDC, a secondary oscillator as an operating oscillator for the electronic system;
• and
• clocking, with the secondary oscillator, the electronic system;
• wherein the OFDC is configured to detect, independent of control signals received from other circuitry, a steady-state voltage on an oscillator output, the OFDC further configured to, in response to detecting the steady-state voltage, output an oscillator failure signal on a reference fail output (RFO).