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A program loader using a cassette magnetic tape

Euromicro Newsletter
Publication Date
DOI: 10.1016/0303-1268(79)90081-6
  • Computer Science


Abstract This paper describes the implementation of a program loader using a cassette magnetic tape. The following patterns make it original: 1. (1) Using a 25 feet tape and 256 octets records, the device makes it possible to address, and read or rewrite any of the 32 records written on the tape. 2. (2) The recording code using two complementary NRZI tracks, instead of one and a clock track, exhibits an excellent redundancy and a symmetrical fitting-up. 3. (3) A special care was brought to restoring the clock signal. This is regenerated through a PLL integrated circuit fed with signals from heads. 4. (4) The loader uses common audio-frequency heads and a quite cheap common sound recorder transport. The data transfer rate is 3000 bits/s at a recording density of 800 BPI. The reliability may be appreciated through a checking routine, the programming of which involves the whole content of a randomly recorded 300 feet tape, that is to say 216 k octets. So far, the number of mistakes that have been tracked down through this routine, has not been large enough to provide any significant result in evaluating this mistake rate. As a conclusion, a statement is made that the digital recording cross-like point is restoring a very reliable clock signal.

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