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