Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Exclusive OR Data Manipulation for Cyclic Code Generation

IP.com Disclosure Number: IPCOM000075227D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Dixon, JD: AUTHOR

Abstract

Exclusive 0R comparisons between bytes of data are obtained despite the lack of "Exclusive 0R" instructions or processor capability. The bytes are utilized to control mask settings for "set bits on" SBN instructions and "set bits off" SBF instructions in a subroutine sequence, which ultimately produces the Exclusive OR result. The cyclic code to be appended to a multiple-byte block is produced by multiple sequences of this subroutine through loop operations.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 73% of the total text.

Page 1 of 1

Exclusive OR Data Manipulation for Cyclic Code Generation

Exclusive 0R comparisons between bytes of data are obtained despite the lack of "Exclusive 0R" instructions or processor capability. The bytes are utilized to control mask settings for "set bits on" SBN instructions and "set bits off" SBF instructions in a subroutine sequence, which ultimately produces the Exclusive OR result. The cyclic code to be appended to a multiple-byte block is produced by multiple sequences of this subroutine through loop operations.

To illustrate the subroutine, the Exclusive OR resultant between byte A and byte B will be obtained by the set bit off SBF instruction and set bit on SBN instruction. Initially byte A is used as a mask to set bits off in byte B. Then the original byte B is used as a mask to set bits off in byte A. The changed byte B is next used to set bits on in the changed byte A. The resultant byte A then contains the Exclusive OR comparison between the original bytes A and B. Assuming initial conditions of byte A existing in location 100 and byte B in location 200, the following is a flow sequence of the subroutine: 1) move location 100 to mask of instruction SBF 1,

2) move location 200 to mask of instruction SBF 2,

3) SBF 1: use mask to set bits off in location 200,

4) SBF 2: use mask to set bits off in location 100,

5) move location 200 to mask of instruction SBN 1, and

6) SBN 1: use mask to set bits on in location 100.

Location 100 will contain the "XOR" of orig...