Patent ID: 7839016

Claim:
An integrated circuit comprising: core circuitry powered by core power supply circuitry at a core power supply voltage, said core circuitry having a core output; output circuitry powered by output power supply circuitry, said output power supply circuitry being controlled separately from said core power supply circuitry, and coupled to said core circuitry to receive a core signal from said core output, said output circuitry being at least partially dependent upon said core signal to generate an output signal having one of a plurality of different output states; voltage sensing circuitry coupled to said core power supply circuitry and responsive to sensing of said core power supply voltage falling below a threshold level to assert a voltage-low signal; a mode signal store configured to receive a retention preselecting signal, said mode signal store being responsive to said retention preselecting signal to store a mode signal indicative of whether or not said retention preselecting signal indicates that signal retention is preselected; wherein said output circuitry, said voltage sensing circuitry, and mode signal store are configured such that said output circuitry is responsive to asserting of said voltage-low signal when said mode signal indicates retention is preselected to maintain a current output state of said output signal independently of said core signal.