Patent ID: 7873896

Claim:
State storage circuitry comprising: an operational data input for receiving input data, a diagnostic data input for receiving diagnostic data and a diagnostic select signal input; a storage element for storing a value indicative of data received from one of said operational data input and said diagnostic data input; an output for outputting said value stored in said storage element; a pulse generator for generating pulses in response to a clock signal, said pulse generator comprising a diagnostic output and a functional output and being responsive to receipt of a diagnostic enable signal at said diagnostic select signal input to output said generated pulses at said diagnostic output and not to output said generated pulses at said functional output and being responsive to receipt of a diagnostic disable signal at said diagnostic select signal input to output said generated pulses at said functional output and not to output said generated pulses at said diagnostic output; an operational path switch for receiving said pulses from said functional output and being responsive to receipt of each of said pulses to provide a transmission path from said operational data input to said storage element and being responsive to receipt of no pulse to isolate said storage element from said operational data input; and a diagnostic path switch for receiving said pulses from said diagnostic output and being responsive to receipt of each of said pulses to provide a transmission path from said diagnostic data input to said storage element and being responsive to receipt of no pulse to isolate said storage element from said diagnostic data input.