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# Method for Generating Parity While the Rotate/Merge Unit is Functioning

IP.com Disclosure Number: IPCOM000037973D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

IBM

## Related People

Huffman, AE: AUTHOR [+3]

## Abstract

A rotate/merge unit is a section of logic that can rotate a data field and merge the field with a second data to produce one field. In accordance with this method, parity is generated while the Rotate/Merge Unit (hereinafter called "RMU") is manipulating the data instead of waiting for the RMU to complete its function. This method of generating parity is called "parity predict".

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Method for Generating Parity While the Rotate/Merge Unit is Functioning

A rotate/merge unit is a section of logic that can rotate a data field and merge the field with a second data to produce one field. In accordance with this method, parity is generated while the Rotate/Merge Unit (hereinafter called "RMU") is manipulating the data instead of waiting for the RMU to complete its function. This method of generating parity is called "parity predict".

The parity predict circuit takes the same input as the RMU, i.e., an input field, an alternate field, a shift amount, a left/right control value and a mask value. From these inputs, the byte parity of the output field is obtained. An actual implementation of the rotate and merge unit only needs to be logically equivalent to the RMU described hereinafter.

That portion of the RMU dataflow that is called the "merge" performs a bit-by- bit selection between the Rotator Output and the Alternate Field as dictated by the Mask in order to produce the Output Field.

In this arrangement, the Rotator Output Predictor is not a true predictor, but is a pseudo-predictor, because it produces a bit-by-bit that does not correspond to the actual Rotator Output. All of the values of the bytes in a bit of actual Rotator Output are present in the same byte of the pseudo-Rotator Output, but they are not in the same order. To get them in the same order, the Mask is rotated on a byte basis in the opposite direction.

Instead of doing a merge o...