Patent ID: 6441985
Filing Date: 2002-08-27
Classification: G11B

Abstract:
A method of detecting velocity of a tape in a capstanless tape transport system having a write head for writing data records to a single track of the tape and for writing discrete format marks to the single track periodically throughout the data records to format the data records being written to the tape by marking periodic intervals and boundaries of the data records and a read head for reading the data records and the discrete format marks written to the tape, the read and write heads separated by a known distance, the method comprising the steps of:(a) receiving a write signal indicating when a discrete format mark is written to the tape by the write head; (b) receiving a read signal indicating when said discrete format mark is read from the tape by the read head; (c) determining the time between receipt of said write signal and said read signal, comprising the steps of: i. starting a first accumulator stage on receipt of a first write signal to generate a count value; ii. when a first read signal is received, reading said count value generated by said first accumulator stage; and iii. when a second write signal is received before said first read signal, starting a second accumulator stage on receipt of a second write signal to generate a second count value; shifting said second count value from said second accumulator stage to said first accumulator stage upon receipt of said first read signal, and reading said second count value from said first accumulator stage upon receipt of a second read signal; and (d) determining the velocity of the tape based on said time determined in step (c) and the known distance between said write head and said read head.