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Redundancy Checking by Table Look Up

IP.com Disclosure Number: IPCOM000074307D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Jones, JW: AUTHOR

Abstract

Function tables held in an associative store 1 are used for redundancy checking. The store comprises four-state cells capable of assuming 1, 0, X and Y states. The X state never gives a mismatch to an associative search operation whereas the Y state always does. A row of the store containing a cell in the Y state can never directly be selected. A 'Next' operation is defined on the store in which the next lower row to a row matching the search argument is selected by a Search, Next operation. In the figures, cells are represented by their states. Cells in the X state are not shown. Multiple matches are read out simultaneously.

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Redundancy Checking by Table Look Up

Function tables held in an associative store 1 are used for redundancy checking. The store comprises four-state cells capable of assuming 1, 0, X and Y states. The X state never gives a mismatch to an associative search operation whereas the Y state always does. A row of the store containing a cell in the Y state can never directly be selected. A 'Next' operation is defined on the store in which the next lower row to a row matching the search argument is selected by a Search, Next operation. In the figures, cells are represented by their states. Cells in the X state are not shown. Multiple matches are read out simultaneously.

Fig. 1 shows the arrangement for vertical redundancy checking of an eight-bit word. Associative store 1 has an I/O register 2 and operates to a store cycle of Search, Next, followed by Read, over all fields of the I/O register. The data to be checked is entered serially-by-bit in the leftmost bit position of register 2, overwriting the previous contents of this position. Initially the register is clear, except for a count of 1000 in the Count field. On each cycle the count is increased by one, the incoming data is stopped across the data field one position to the right, and the partial parity is read into field P' of register 2. A final count of 1000 and a P field of 0 indicates that the parity of the received data is correct.

A similar technique can be used for longitudinal redundancy checking.

An example of cyclic redundancy checking using CRC-16...