Patent EP-0127118-B1 (EP)
IPC: G06F11/10
Filed: 1984-05-22
Granted: 1988-05-11
Abstract: 1. A Store control arrangement (Fig.1) - in particular for an error-tolerant telephone exchange system - for determining the freedom from errors of the address (Adr) and, if possible, for correcting the stored word (Infout) when this stored word (Infout) is read-out from a store (Mem) where - a section of a word (Infin), composed of digits or bits, generally comprises only a sub-quantity, formed for example by a mask, of the digit positions of this work (Infin), - the stored word (Infin, Infout) is protected section by section, e.g. in accordance with an SEC-DED - method, by means of parity digits (PBinf) in that each digit position of the stored word (Infin, Infout) is contained in a plurality of overlapping sections of the stored word (Fig.2) and in that a plurality of parity digit generators (PG1...PG6) are provided which each generate a parity digit, section by section, from digits, intermediately stored in a stored word digit storage cell, of the stored word (Infin, Infout), - the number of parity digit generator (PG1...PG6), which are each connected by one of their inputs to the stored word digit storage cell for a digit position of the stored word (Infin, Infout), and thus the number of sections which contain the respective digit position of the stored word (Infin, Infout) is in each case finite and odd-numbered, - the address is likewise protected in that from digits, intermediately stored in a respective address digit storage cell, of individual sections of the address the parity (PBadr) of the individual sections is determined by parity digit generators (PG1...PG6), - at the time of the input of the stored word (Infin) the parity digits (PBin), produced from the address (Adr) and the stored word (Infin), are stored in special storage locations of the store (Mem) assigned to each stored word (Infin), - at the time of the read-out of the stored word (Infout) the parity digits (PBout), stored in the respective special storage locations, are supplied, together with the respective address (Adr) and/or the parity digits (PBadr) determined from this address (Adr), to an error determining and correcting circuit (EDC) which (EDC) itself checks the correctness of the address (Adr) used for read-out, and which also checks the correctness of the read-out stored word (Infout), e.g. in accordance with an SEC-DED - method by means of syndromes formed the parity digits (PBadr, PBout) and, in the event that the read-out stored word (Infout) contains an error, if possible corrects this error, in that at least - in the error determining and correcting circuit (EDC) single errors in the stored words (Infout), derived from the syndrome are in each case corrected, - but errors in the address (Adr) derived from the syndromes an multiple errors in the stored word (Infout) derived from the syndrome trigger an alarm and/or a repetition of the read-out procedure, caracterized in that - the address (Adr) is also protected section by section by means of parity digits in such manner that each digit position of the address (Adr) is contained in a plurality of overlapping sections of the address (Adr) which are each checked independently by parity formation, - each section of the address (Adr) generally comprises only a sub-quantity, formed for example by a mask, of the digit positions of the address (Adr) (Fig.2) and - the number of parity digit generators (PG1...PG6), which are each connected by one of their inputs to the address digit storage cell for a digit position of the address (Adr), and thus the number of sections containing this respective digit position of the address (Adr) - is in each case finite and even-numbered.