In-system testing of an oscillator

A method for testing a signal generator for a circuit on a circuit board, the method comprising:

• powering the signal generator;
• initiating a test mode for the circuit;
• and
• in the test mode, selectively passing a signal from the signal generator to a port of the circuit for testing the signal form the signal generator.

A method of testing electronic devices on a circuit board with a clock signal, the method comprising:

• coupling a clock signal to a microprocessor;
• coupling a test signal to the microprocessor;
• passing operation instructions and the clock signal to a multiplexer in response to the test signal;
• multiplexing the clock signal through the multiplexer to an external access port in response to the operation instructions;
• and
• measuring the frequency of the clock signal at the external access port.

A circuit board testing system, the testing system comprising:

• an external tester adapted to generate test instructions;
• a circuit board comprising,
• a microprocessor selectively coupled to receive the test instructions from the external tester, wherein the microprocessor goes into a test mode upon receiving the test instructions from the external tester,
• an oscillator to provide a clock signal,
• a field programmable array (FPGA) to provide operational functions of the circuit board, and
• a multiplexer contained in the FPGA, the multiplexer is coupled to receive the clock signal, the multiplexer is further coupled to receive operational instructions from the microprocessor when the microprocessor is in the test mode, wherein the multiplexer multiplexes the clock signal to an external access port in response to receiving the operational instructions from the microprocessor;
• and
• a measuring device selectively coupled to the external access port to measure the frequency of the clock signal at the external access port, wherein if the frequency of the clock signal at the external access port matches an expected frequency the oscillator is verified as working properly.

An electronic module with testing functionality, the electronic module comprising:

• a microprocessor adapted to receive test instructions from an external tester, wherein the microprocessor goes into a test mode upon receiving the test instructions from the external tester;
• a signal source coupled to the microprocessor to provide a signal;
• a functional circuit operatively coupled to the microprocessor to provide operation functions of the electronic module in non-test modes;
• and
• a multiplexer in contained in the functional circuit adapted to receive the signal from the microprocessor, the multiplexer is further coupled to receive operation instructions from the microprocessor when the microprocessor is in the test mode, wherein the multiplexer multiplexes the signal to an external access port in response to receiving the operational instructions from the microprocessor in test mode.