Data transducer positioning system with an overrun prevention capability

Abstract

A data storage and retrieval system is disclosed which includes a transducer for data transfer with a rotating magnetic disk having a multiplicity of addressable annular data tracks formed concentrically on at least one of the major surfaces thereof. The transducer reads the prerecorded addresses on the successive data tracks being traversed during each track seeking operation. Periodically sampling the track addresses being read by the transducer, a microprocessor determines the data track on which the transducer is currently positioned, and computes the remaining number of tracks to be traversed until the transducer arrives at a destination track. Should there be errors in the track address samples, due for example to the failure of the transducer to read some track addresses, the microprocessor might become unable to determine the correct current transducer position, with the consequent possibility of transducer overrun beyond the data storage zone on the disk surface. The seek operation is therefore discontinued immediately when a prescribed number of errors are found in the track address samples and in sector pulses that determine the sampling intervals. Additional embodiments are disclosed in which track seeking operation is stopped when the transducer has just overrun the data storage zone.