Browse Prior Art Database

Data Nibblize and Denibblize Circuitry

IP.com Disclosure Number: IPCOM000034600D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Wu, RH: AUTHOR

Abstract

Disclosed is a circuit that nibblizes and denibblizes binary data in the communication between a host computer and a personal computer through an IBM 3174 or 3274 communication controller. The communication controller is operated by a set of binary commands which are indistinguishable from the actual data that it is supposed to transfer. One way to distinguish commands and the actual data is to transform the data into another format before going into the controller, and retransform the data back after coming out of the controller. The processes of transforming and retransforming are called nibblization and denibblization, respectively. This disclosure uses a 3 to 4 nibblization scheme with a 4 to 3 denibblization scheme.

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Data Nibblize and Denibblize Circuitry

Disclosed is a circuit that nibblizes and denibblizes binary data in the communication between a host computer and a personal computer through an IBM 3174 or 3274 communication controller. The communication controller is operated by a set of binary commands which are indistinguishable from the actual data that it is supposed to transfer. One way to distinguish commands and the actual data is to transform the data into another format before going into the controller, and retransform the data back after coming out of the controller. The processes of transforming and retransforming are called nibblization and denibblization, respectively. This disclosure uses a 3 to 4 nibblization scheme with a 4 to 3 denibblization scheme. The nibblization scheme transforms 3-byte raw data into 4-byte nibblized data by inserting 2 leading bits of zero into each byte. Likewise, 2-byte or 1-byte raw data are transformed into 3- or 2-byte nibblized data, respectively. The denibblization scheme retransforms 4-byte nibblized data into 3-byte raw data by removing the 2 leading bits of zero from each byte. Likewise, 3-byte or 2-byte nibblized data are retransformed into 2-byte or 1-byte raw data, respectively. The control signals of this circuit include CLK1(clock), NIB(nibblize), DNB(denibblize) and CLEAR. Based on the control signals and a timing logic, this circuit inputs 3 bytes of raw data in sequence for nibblization. After 1 clock cycle delay,...