Enhanced reliability data storage system with second memory for preserving time-dependent progressively updated data from destructive transient conditions

Claim 1

Apparatus for preserving time-dependent, progressively updated, critical information from destruction by the adverse effects produced by an externally originated transient condition, comprising: (a) a first storage means for holding said critical information; (b) means for collecting said critical information from said first storage means; (c) a second storage means substantially immune to said adverse effects; (d) means for entering said collected critical information in the form of successive critical information frames into said second storage means, said critical information including at least one complete frame comprised of progressively updated critical data words and a progressively updated time word representative of the elapsed time starting from a predetermined reference point, said frame further including information adapted to provide a recovered bit clock signal; (e) said first storage means comprising a scratch pad memory and a timer adapted to store said critical data words and said updated time words respectively, said timer including a clock adapted to generate clock pulses and a counter for storing and progressively updating said time word by advancing said counter in synchronism with said clock pulses; (f) said collecting means including means for providing successive readouts from said scratch pad memory and said timer, each of said readouts being adapted to provide at least one of said critical information frames comprising said critical data words and said time word; (g) said second storage means including means for imposing a predetermined delay interval extending from the entry of said critical information therein to its retrieval therefrom, said delay interval having a duration selected to assure the presence, in said second storage means, upon the termination of the adverse effects, of said critical information that was entered before the onset of said transient condition; (h) means for discarding said critical information retrieved from said second storage means during a normal mode of operation of said apparatus; and (i) means for retrieving and reloading said critical information from said second storage means into said first storage means after the termination of said adverse effects during a recovery mode of operation of said apparatus initiated by the onset of said transient condition, said retrieving and reloading means further comprising means for resynchronizing said clock with said recovered bit clock signal and for simultaneously reloading said time word into said counter during said recovery mode of operation.