Computer Peripherals, Inc.

Normand E Precourt

A data writing and recording system and method and circuitry therefor is disclosed in which peak shift due to pulse crowding of data recorded on a magnetic medium is substantially reduced. The recorded data time pattern is preemphasized to compensate for peak shift such that an optimum magnetic pattern is recorded on the magnetic medium. The preemphasis of recorded peak shift errors is accomplished either by delaying or advancing the time when a particular peak shifted data transition caused by a known encoding data pattern will occur. NRZI type encoded data is coupled to a first serial to parallel shift register and clocked through to a ROM at a frequency corresponding to the data bit cell width. The ROM examines the incoming data, which is also clocked from an intermediate stage in the first shift register to a second serial-to-parallel shift register having a data clock frequency substantially greater than the data clock frequency of the first shift register. The second shift register operates as a multi-tapped delay line having a multiplexed output selected by a look-up table programmed into the ROM in accordance with a determination by the ROM of the degree incoming peak shift and the amount of compensation required. Thus, data is either delayed or advanced before it is written, thereby compensating for peak shift error which would otherwise be present in the recorded data.

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Norristown, PA, United States of America

Normand E Precourt