Scanning Data to Find a Key Sequence
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
A data processor must frequently scan a real-time data stream from a disk file or other device to find a sequence of key bytes (or a higher- valued or lower-valued sequence). Normally, this requires hardware registers and a large amount of hardwired logic, since purely microcoded scans are too slow. Fig. 1 shows a fast logic 10 which uses significantly less hardware and is easier to use. When a scan command is issued, the user specifies the key value, the type of scan to be performed (high, low, equal), and certain parameters that describe where the keys are to be positioned in a 256-byte sector for comparison against the file: length of the key, the separation between the keys, the starting position for the first key, and the ending position for the last key.