Harvard biphase is a magnetic run length code for encoding magnetic tape.Digest of papers: computer peripherals, CPU--benefactor or bottleneck?, IEEE Computer Society, 1974 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. 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.
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.Digest of Papers, Institute of Electrical and Electronics Engineers, 1974 The data are encoded in frames and each of these contains a snapshot of the avionics system in the aircraft. 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.Digital Equipment Computer Users Society Digital Equipment Corporation, 1975 - Electronic digital computers The ARINC 573 serves as a standard for FDRs that feature continuous data stream encoded in Harvard biphase.
See also ARINC 573
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