Anthony Samuel Schiavo

US Patent:

48991473, Feb 6, 1990

Filed:

Jun 3, 1988

Appl. No.:

7/202733

Inventors:

Anthony P. Schiavo - Lafayette Hill PA
Paul H. Selby - Norristown PA
Harold L. Gibson - Lansdale PA

Assignee:

Unisys Corporation - Blue Bell PA

International Classification:

H03M 730

US Classification:

341 60

Abstract:

A data compression/decompression apparatus employs common circuitry and a single string table for compression and decompression. A throttle control is provided to prevent data under-runs and an optimizing start-up control delays the start-up of the recording device until the compression apparatus has compressed sufficient data to effeciently reduce throttling and loss of compression when the output device is started. The decompression apparatus may operate to decompress compressed data when the compressed data is read in either the same direction as it was recorded, or read in the direction reverse to that in which it was recorded. A further feature is the provision of a counter which is incremented by one after a predetermined number of string codes have been written into the string table. The output of the counter is stored in the string table with each string code and prefix code. When searching for an empty or usable location in the string table, the count value read from the location is compared with the count in the counter.