Track crossing method using dual counters

A method of controlling the tracking head in a recording/playback device to cause said tracking head to cross a selected number of data tracks in a data medium when traveling in a desired direction comprising the steps of:

• factoring said selected number into components X2.sup.k +R where X, k and R are integers and R is the remainder of the selected number minus X2.sup.k, and establishing first and second count values having a difference R;
• incrementing/(decrementing) said first count value each time said tracking head crosses a data track when traveling in a direction opposite said desired direction;
• incrementing/(decrementing) said second count value each time said tracking head crosses a data track when traveling in said desired direction;
• comparing the incremented/(decremented) first and second count values and providing a control signal when said incremented/(decremented) first and second count values are equal;
• monitoring said control signal for determining the occurrence of R track crossings in the desired direction;
• successively establishing said first and second count values with a difference 2.sup.k, each time the control signal indicates that 2.sup.k track crossings have occurred in the desired direction;
• and
• counting the number of occurrences that the control signal indicates that 2.sup.k track crossings in the desired direction have occurred and providing a stop signal to said tracking head after X indications of said 2.sup.k track crossings.

A method of controlling the tracking head in a recording/playback device to cause said tracking head to cross a selected number of data tracks in a data medium when traveling in a desired direction comprising the steps of:

• establishing a first count value representative of said selected number to a value equal to the selected number of data tracks to be crossed minus M where M is an integer representative of the number of data tracks over which said tracking head will drift due to inertia;
• incrementing/(decrementing) said first count value each time said tracking head crosses a data track when traveling in a direction opposite said desired direction;
• establishing a second count value which is different from said first count value by an amount equal to said selected number and incrementing/(decrementing) said second count value each time said tracking head crosses a data track when traveling in said desired direction;
• comparing the incremented/(decremented) first and second count values and providing a control signal to said tracking head when said incremented/(decremented) first and second count values are equal.

Apparatus for controlling the number of data tracks crossed by a tracking head of a recording/playback device as said tracking head moves in a desired direction over a recording medium, comprising:

• a source of track crossing pulses indicating the occurrence of respective track crossings;
• a source of a control signal which indicates the direction of said respective track crossings;
• first and second counters having respective output ports for providing count values, and having respective input terminals for applying counting signals, said first and second counters incrementing/decrementing their respective count values responsive to pulses applied to their respective input terminals;
• means for presetting the first and second count values of said first and second counters such that they exhibit a difference corresponding to said number of data tracks;
• means responsive to said control signal for applying track crossing pulses to said first counter when said control signal indicates track crossings correspond to a first direction, and for applying track crossing pulses to said second counter when said control signal indicates track crossings correspond to a second direction, and
• comparator means coupled to the output terminals of said first and second counters, for providing a signal indicating equality of the count values provided by said first and second counters.

Apparatus for controlling the number of data tracks crossed by a tracking head of a recording/playback device as said tracking head moves in a desired direction over a recording medium, comprising:

• a source of track crossing pulses indicating the occurrence of respective track crossings;
• a source of a control signal which indicates the direction of said respective track crossings;
• first and second counters having respective output ports for providing count values, and having respective input terminals for applying counting signals, said first and second counters incrementing/decrementing their respective count values responsive to pulses applied to their respective input terminals;
• means responsive to said number of tracks for factoring said number to generate the integers X and R corresponding to the values in the relation given by
• number=X2.sup.k +R
• where k is an integer and 2.sup.k is a value less than the maximum count value that can be provided by said first and second counters;
• means for presetting the count values of said first and second counters to a difference equal to R.
• means responsive to said control signal for applying track crossing pulses to said first counter when said control signal indicates track crossings correspond to a first direction, and for applying track crossing pulses to said second counter when said control signal indicates track crossings correspond to a second direction;
• comparator means coupled to the output terminals of said first and second counters, for providing a signal indicating equality of the count values provided by said first and second counters;
• and
• means for resetting the count values of said first and second counters to a difference of 2.sup.k on the occurrence of said comparator means indicating said equality.