Abstract: An emulation unit/target processor interface apparatus senses the target processor I/O voltages using filters to reduce the noise level and provides the rest of the interface apparatus with a target reference voltage level. The reference voltage is used to create threshold voltages, termination voltages and drive levels appropriate to provide an interface with the target processor. Power loss in the target processor is also detected so that drive signals can be removed from the target processor to avoid damaging the target processor and to prevent the target processor from being energized by the emulation unit.

Abstract: In plurality of series-coupled circuit boards, a thermometer code is used to provide the address signals for the circuit board. Each terminal of the circuit board input connector is coupled next successive terminal of the circuit board output connector. The terminals of the circuit board input connectors are coupled, through a pull-up resistor, to a voltage source. The least significant terminal of the output terminal can provide a logic signal opposite to the logic signal provided by the voltage source. The address lines for the circuit board are coupled to the terminals of the input connector. In this manner a thermometer address code can be provided for the sequence of series-coupled circuit boards. According to the present invention, the thermometer codes can be expanded with selected additional apparatus.

Abstract: A heating pad controller is provided which varies the duty cycle during which power is applied to a heating pad heating element. In one embodiment according to the present invention, an oscillator circuit is used to vary the off-time of the duty cycle, with the on-time portion being fixed. User control of the off-time is provided by way of a rotary control knob connected to a potentiometer. The potentiometer is part of the oscillator circuit and is used to vary the resistance through which a capacitor in the oscillator circuit charges up. The output of the oscillator circuit is used to control the gate of a silicon controlled rectifier (SCR), which acts as a power switch through which power is applied to the heating element. During power up, the oscillator circuit is overridden and a continuous control signal is applied to the SCR to provide constant power to the heating element to thereby achieve rapid heating.