Abstract: An information data detecting apparatus for use in a recording medium playing apparatus detects the presence/absence of information data under software control using an error correction code. The information data detecting apparatus acquires a read signal representing the contents of a specified sector, extracts digital data from the read signal, performs an error-correcting operation on the extracted digital data and produces an error-correctable indicating flag when error correction is possible. When detecting the presence of the error-correctable indicating flag, the information data detecting apparatus produces a written-state signal indicating that the specified sector is used.

Abstract: A microcomputer having an error correction function includes a summing function for calculating a total-sum of data associated with a block of stored data, a total-sum changing function for calculating a new total sum of data associated with the block of stored data when new data is stored in the block of stored data, the new total sum of data being based on an equation S.sub.new =S.sub.old +X.sub.new -X.sub.old, where, X.sub.new denotes new data replacing old data X.sub.old, and S.sub.

Abstract: The invention provides a method and apparatus for logging all references to microstore addresses irrespective of the number of times that a same address is referenced and irrespective of the order in which addresses are referenced. It provides a log indicating simply whether each address of the microstore has or has not been referenced within a prescribed time period. There is no limit placed on the duration of the prescribed time period and thus logging can cover long-term events such as, the full execution of a single macro-instruction, the full execution of an assembly level routine or the execution of all micro-instructions resident in the microstore as they are subjected to all possible input parameters. A practical tool for global visualization of computer operations is therefore provided.

Abstract: A method in which the boundary-scan circuitry of a boundary-scan chain is placed in a first condition in which each bit of a series of bits will traverse a path through an equipment identification register if one exists or will require one clock to traverse each device in the boundary-scan chain in which no complete identification register exists. A first recognizable series of bits is sent through the chain and the beginning of the series of bits is detected at the output of the chain while a count is kept at the output to determine the number of individual boundary-scan circuits in the chain. The count is incremented by one for each identification register traversed or for each circuit which has no such complete register.

Abstract: A method for rewriting four defect management areas on an optical disk according to an ECMA standard is performed by means of deleting an old data which has been recorded on the respective defect management areas and then sequentially writing down a new data on respective defect management areas.

Abstract: A symbol interleaving method for organizing data in a semiconductor memory such that fault tolerance of the memory is optimized when used in conjunction with a Reed-Solomon burst error correcting code. The Reed-Solomon symbols are aligned with respect to the bus bits of the memory such that the impact of a bus bit failure that affects all memory devices in the memory using the bus is constrained within the correction capability of the ECC. The symbols also are distributed among the memory devices in order to maximize fault tolerance. Up to two memory devices in the preferred embodiment may fail without exceeding the correction capability of the code.

Abstract: Decoding power is enhanced by (1) flagging only those codewords where the ECC capability has been exceeded; (2) permitting codewords to be of any byte length (n) and codeword depth (.lambda.) subject only to the requirement that n and .lambda. be relatively prime; and (3) interleaving encoded bytes of successive codewords diagonally in a single continuous sequence to form an array with a toroidal topology so that all burst errors will be continuous from codeword to codeword, irrespective of where they occur in the array. These attributes assure that there will never be a problem with burst errors affecting.ltoreq..lambda. rows because there is no "last row" and "first row".