Real time software implementation of a multipack digital tape recorder data channel

The bandwidth of a stationary-head digital tape recorder may be increased by adopting a multitrack format. A number of problems exist, however, which are associated with the effective tape/tape-head transport. These include, tape velocity and azimuth variation, tape deformation and dropouts. These problems can be compensated for by employing intelligent software techniques. The inherent parallelism of the microprocessor can be utilised so that each bit of the processor´s word is used to process the data of one track. This would permit low cost mechanical components and tape to be used. This philosophy has been applied to a basic compact-cassette tape transport and tape controlled from a Z80-based microprocessor. The processor handles all encoding/decoding, synchronising, track-sampling and error-correction functions. Adaptive software allows for tape velocity and azimuth variations and data detection is enhanced by a software sampling technique which emulates the operation of a phase-locked loop