Browse Prior Art Database

Cassette Data Format

IP.com Disclosure Number: IPCOM000088062D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 18K

Publishing Venue

IBM

Related People

Vautier, R: AUTHOR

Abstract

Interface adapters designed to connect terminals to a packet switching network have their control program implemented in a read-only storage. This program can be loaded from a cassette recorder. This article describes the format of the recorded data and the way these data are written on the cassette tape to allow an easy clock and data recovery when reading the tape.

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Cassette Data Format

Interface adapters designed to connect terminals to a packet switching network have their control program implemented in a read-only storage. This program can be loaded from a cassette recorder. This article describes the format of the recorded data and the way these data are written on the cassette tape to allow an easy clock and data recovery when reading the tape.

The data are recorded on tape in bipolar code. The requirement of clock recovery is achieved with an SDLC (synchronous data link control) format by coding 0 bits alternatively by positive and negative pulses, whereas 1 bits are coded with no pulses.

During the frame of data, the minimum zero density is assumed by the zero insert replacing the sixth 1 bit of the SDLC system. In the idle state, a sequence of continuous flag characters (see figure) is transmitted. Thus, the maximum "1" sequence length, during which clock recovery is not possible, is six with the flag character 0 1 1 1 1 1 1 0.

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