Harvard biphase

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Harvard biphase is a magnetic run length code for encoding magnetic tape. [1] It is one of the formats employed in forming the digital bits of logic one and logic zero, along with non-return-to-zero (NRZ) and bipolar-return-to-zero (RZ) formats. [2] Each bit in the Harvard biphase format undergoes change at its trailing edge and this transpires either from high to zero or zero to high independently of its value. [2]

Contents

FDR

Harvard biphase has previously been used for digital flight data recorder (FDR) where 12-bit words per second are recorded onto magnetic tape using Harvard biphase code. [3] The data are encoded in frames and each of these contains a snapshot of the avionics system in the aircraft. [4] For Harvard biphase, a phase transition in the middle of the bit cell indicates that the bit is 1. No transition indicates that the bit is 0. There is also a phase transition at the start of each bit cell. [5] The ARINC 573 serves as a standard for FDRs that feature continuous data stream encoded in Harvard biphase. [6]

See also

References

  1. ↑ Digest of papers: computer peripherals, CPU--benefactor or bottleneck?, IEEE Computer Society, 1974
  2. 1 2 Wyatt, David; Tooley, Mike (2009). Aircraft Electrical and Electronic Systems . Oxford: Butterworth-Heinemann. pp.  328. ISBN   9780750686952.
  3. ↑ Digest of Papers, Institute of Electrical and Electronics Engineers, 1974
  4. ↑ "BMC COMMUNICATIONS CORP". bmccorp.com. Retrieved 2019-07-18.
  5. ↑ Digital Equipment Computer Users Society Digital Equipment Corporation, 1975 - Electronic digital computers
  6. ↑ Tooley, Mike; Wyatt, David (2012-08-21). Aircraft Digital Electronic and Computer Systems. Oxon: Routledge. p. 42. ISBN   9780750681384.


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