Method and apparatus for determining the format of a magnetic tape and for presetting a magnetic head to a reference track thereof

Abstract

A magnetic tape drive has firmware which has been modified so that the drive will read both standard formal tapes and non-standard format tapes. Non-standard tapes are detected by an absence of reference bursts in the load zone of the tape. The head is moved to successive tracks toward the edge of the tape until no data is read. This identifies the track near the edge of the tape. Then, the head is preset to a track which is a known distance from the edge of the tape. Reading of non-standard tapes is accomplished by disabling the index pulse generator in the intervals between data segments. The performance of a SKIP COMMAND is made possible by counting the transitions of data to no data during the intervals between data segments. The identification of different types of non-standard formats is made by determining the length of the data segments.

What is claimed is: 
     
       1. In a magnetic tape drive for digital computer backup of the type in which a magnetic head is moved across a magnetic tape to read digital data on longitudinal tracks between the .Iadd.lateral .Iaddend.edges of said magnetic tape, said longitudinal tracks having load zone and data zone portions, .[.the.]. .Iadd.a .Iaddend.method of presetting said magnetic head to a reference track on tapes written .[.on both standard and non-standard formats.]. .Iadd.in either a first format or an other format .Iaddend.comprising: reading a load zone portion .Iadd.and a data zone portion .Iaddend.of said tape;   determining .[.the format of said data in said load zone to determine.]. .Iadd.from reading said load zone and said data zone portions .Iaddend.whether said tape is written in said .[.standard.]. .Iadd.first .Iaddend.format .[.or a non-standard.]. .Iadd., said other .Iaddend.format.[.;.]. .Iadd., or is unformatted, said performing the following additional steps if the determined format is said other format: .Iaddend.   moving said head .[.to.]. .Iadd.over .Iaddend.successive .Iadd.longitudinal .Iaddend.tracks toward one .Iadd.lateral .Iaddend.edge of said tape .[.if the determined format is non-standard.].;   .[.reading data.]. .Iadd.detecting whether data is present .Iaddend.in the data zones of said successive .Iadd.longitudinal .Iaddend.tracks .Iadd.as said head moves toward said one lateral edge.Iaddend.;   identifying .[.the.]. .Iadd.the location of said one lateral .Iaddend.edge of said tape when .[.no.]. data is .[.read.]. .Iadd.no longer detected.Iaddend.; and   moving said head a .[.known.]. .Iadd.predetermined .Iaddend.distance from .[.the edge of said tape to said.]. .Iadd.said identified location to the .Iaddend.reference track .Iadd.of said other format. .Iaddend.   
     
     
       2. The method recited on claim 1 wherein said tape drive is connected through an interface to a controller and host computer and wherein .[.said standard.]. .Iadd.the first .Iaddend.format .[.tape.]. is written in segments of data along each of said .Iadd.longitudinal .Iaddend.tracks, wherein there are relatively large blank gaps between said segments, and wherein an index pulse at the end of each gap signifies the start of each data segment, .[.the method of reading data from non-standard tapes which have.]. .Iadd.and further wherein said other format has .Iaddend.relatively small blank gaps between data segments and irrelevant data in the remaining portion .[.of the track.]. between the data segments .Iadd.of each longitudinal track, said method further .Iaddend.comprising .Iadd.the following additional steps when the determined format is said other format.Iaddend.: detecting said relatively small blank gaps;   timing out the remainder of a time interval between data segments in response to said detection; and   generating an artificial index pulse at the end of the timing out, said index pulse being supplied to the interface of said tape drive.   
     
     
       3. The method recited in claim 2 wherein said irrelevant data is servo information. 
     
     
       4. The method recited in claim 3 wherein the step of timing out the remainder of the time interval between data segments comprises: counting data transitions in said servo information; and   enabling the generation of said index pulse after a predetermined number of .[.such.]. .Iadd.said data .Iaddend.transitions have occurred.   
     
     
       5. The method recited in claim 2 wherein .[.the tape drive is connected to a controller by an.]. .Iadd.said .Iaddend.interface .[.which.]. transmits a SKIP command to the tape drive specifying movement of .Iadd.the .Iaddend.tape by a specified number of data segments in the forward or reverse .[.directions.]. .Iadd.direction.Iaddend., said method further comprising performing .[.a.]. .Iadd.the .Iaddend.SKIP command on a .[.non-standard tape.]. .Iadd.tape having said other format .Iaddend.by the steps of: counting said small blank gaps during performance of .[.a.]. .Iadd.the .Iaddend.SKIP command, and   exiting the performance of said SKIP command when the count equals said specified number of data segments.   
     
     
       6. The method recited in claim 2 .Iadd.wherein said tape is written in either said first format or one of a plurality of different types of other formats, the method .Iaddend.further comprising .Iadd.the following steps when the determined format is one of said other formats.Iaddend.: determining the length of said data segments on .[.said non-standard tapes.]. .Iadd.the tape having one of said other formats.Iaddend.; and   indicating the type of .[.non-standard tape.]. .Iadd.said one of said other formats .Iaddend.based on the length of said data segments.   
     
     
       7. In a magnetic tape drive of the type in which a magnetic head is moved across a magnetic tape to read data on longitudinal tracks between the .Iadd.lateral .Iaddend.edges of said magnetic tape, .[.the.]. .Iadd.a .Iaddend.method of presetting said magnetic head to a reference track on .[.tapes.]. .Iadd.a tape .Iaddend.written in .[.both standard and non-standard formats.]. .Iadd.either a first format or an other format, .Iaddend.said .[.standard.]. .Iadd.first .Iaddend.format having load zone and data zone portions and reference bursts in tracks in said load zone.Iadd., said other format having data zone portions but having no such reference bursts in a portion corresponding to the load zone portion of said first format, said method .Iaddend.comprising: .[.reading a load zone portion of said tape;.].   determining whether said tape is written in said .[.standard or a non-standard.]. .Iadd.first format, said other .Iaddend.format .[.from the data read in said load zone.]., .Iadd.or is unformatted .Iaddend.said step of determining including:   searching for said reference bursts in .Iadd.a portion of said tape corresponding to .Iaddend.said load zone .Iadd.portion of said first format;.Iaddend.   providing an indication that said tape is written in .[.a non-standard.]. .Iadd.said first .Iaddend.format if .[.no such.]. reference bursts are detected.Iadd., but if no reference bursts are detected, moving said tape so that said head reads the data zone portion of said tape.Iaddend.;   .Iadd.indicating that said tape is not formatted if no data is read in said data zone portion, but if data is read in said data zone portion, indicating that said tape is written in said other format; and .Iaddend.   .[.moving said head to successive tracks toward one edge of said tape if the determined format is non-standard;   reading data in the data zones of said successive tracks;   identifying the edge of said tape when no data is read; and.].   .Iadd.if the determined format is said other format, .Iaddend.moving said head a .[.known.]. .Iadd.predetermined .Iaddend.distance .[.from the edge of said tape.]. to .[.said.]. .Iadd.the .Iaddend.reference track .Iadd.of said other format.Iaddend..   
     
     
       8. In a magnetic tape drive of the type in which a magnetic head is moved across a magnetic tape to read data on longitudinal tracks between the .Iadd.lateral .Iaddend.edges of said magnetic tape, .[.the.]. .Iadd.a .Iaddend.method of presetting said magnetic head to a reference track on .[.tapes.]. .Iadd.a tape .Iaddend.written in .[.both standard and non-standard formats.]. .Iadd.either a first format or an other format, said first format having load zone and data zone portions and reference bursts in longitudinal tracks in said load zone, said other format having data zone portions but having no such reference bursts in a portion corresponding to the load zone portion of said first format, said method .Iaddend.comprising: reading a .Iadd.portion of said tape corresponding to the .Iaddend.load zone portion of said .[.tape.]. .Iadd.first format .Iaddend.;   determining whether said tape is written in said .[.standard.]. .Iadd.first format .Iaddend.or .[.a non-standard.]. .Iadd.said other .Iaddend.format from .[.the.]. data read in .[.said.]. .Iadd.the portion corresponding to said .Iaddend.load zone .[.;.]. .Iadd.portion, and performing the following steps if the determined format is said other format: .Iaddend.   moving said head .[.to.]. .Iadd.over .Iaddend.successive .Iadd.longitudinal .Iaddend.tracks toward .[.the.]. .Iadd.one lateral .Iaddend.edge of said tape .[.if the determined format is non standard.].;   .[.reading data.]. .Iadd.detecting whether data is present .Iaddend.in the data zones of said successive .Iadd.longitudinal .Iaddend.tracks .Iadd.as said head moves toward said one lateral edge.Iaddend.;   identifying the .Iadd.location of said one lateral .Iaddend.edge of said tape when .[.no.]. data is .[.read.]. .Iadd.no longer detected .Iaddend.; and   moving said head a .[.known.]. .Iadd.predetermined .Iaddend.distance from the .[.edge of said tape.]. .Iadd.identified location .Iaddend.to .[.said.]. .Iadd.the .Iaddend.reference track .Iadd.of said other format.Iaddend., said .[.steps.]. .Iadd.step .Iaddend.of moving said head .Iadd.over successive longitudinal tracks .Iaddend.being carried out in incremental steps across said tape.   
     
     
       9. The method recited in claim .[.7.]. .Iadd.8 .Iaddend.further comprising: moving said tape through said .Iadd.portion corresponding to the .Iaddend.load zone .Iadd.portion of said first format and .Iaddend.into said data zone before the step of .[.reading data.]. .Iadd.detecting whether data is present .Iaddend.in .Iadd.the data zone of said .Iaddend.successive .Iadd.longitudinal .Iaddend.tracks.   
     
     
       10. The method recited in claim 8 wherein the step of moving said head a .[.known.]. .Iadd.predetermined .Iaddend.distance from the .Iadd.identified location of said one lateral .Iaddend.edge of the tape includes moving a fixed number of said incremental steps. 
     
     
       11. The method recited in claim 8 wherein said tape has a beginning of tape marker, said method thereafter comprising the step of: rewinding said tape to the beginning of tape marker on said tape.   
     
     
       12. In a magnetic tape drive of the type in which a magnetic head is moved across a magnetic tape to read data on the longitudinal tracks between the .Iadd.lateral .Iaddend.edges of said magnetic tape, .[.said longitudinal tracks having load zone and data zone portions, the.]. .Iadd.a .Iaddend.method of presetting said magnetic head to a reference track on .[.tapes.]. .Iadd.a tape .Iaddend.written in .[.both standard and non-standard formats.]. .Iadd.either a first format or an other format, said first format having load zone and data zone portions and reference bursts in longitudinal tracks in said load zone, said other format having data zone portions but having no such reference bursts in a portion corresponding to the load zone portion of said first format, said method .Iaddend.comprising: reading a .Iadd.portion of said tape corresponding to the .Iaddend.load zone portion of said .[.tape.]. .Iadd.first format.Iaddend.;   determining whether said tape is written in said .[.standard.]. .Iadd.first .Iaddend.or .[.a non-standard.]. .Iadd.said other .Iaddend.format from .[.the.]. data read in .Iadd.the portion corresponding to .Iaddend.said load zone .[.;.]. .Iadd.portion, and performing the following additional steps if the determined format is said other format: .Iaddend.   moving said head .[.to.]. .Iadd.over .Iaddend.successive .Iadd.longitudinal .Iaddend.tracks toward one .Iadd.lateral .Iaddend.edge of said tape .[.if the determined format is non-standard.].;   .[.reading data.]. .Iadd.detecting whether data is present .Iaddend.in the data zones of said successive .Iadd.longitudinal .Iaddend.tracks .Iadd.as said head moves toward said one lateral edge .Iaddend.of said tape and detecting whether data is present in fixed intervals of reading;   identifying the .Iadd.location of said one lateral .Iaddend.edge of said tape when .[.no.]. data is .[.read.]. .Iadd.no longer detected .Iaddend.; and   moving said head a .[.known.]. .Iadd.predetermined .Iaddend.distance from .[.the edge of said tape.]. .Iadd.said identified location .Iaddend.to .[.said.]. .Iadd.the .Iaddend.reference track .Iadd.of said other format..Iaddend.   
     
     
       13. The method recited in claim 12 wherein the step of moving said head to successive tracks includes moving said head at least one incremental step each time data is detected in one of said fixed intervals of reading. 
     
     
       14. The method recited in claim 13 wherein the step of identifying the .Iadd.location of said one lateral .Iaddend.edge of said tape occurs when .[.no.]. data is .Iadd.no longer .Iaddend.detected in said fixed intervals. 
     
     
       15. A magnetic tape drive of the type in which a magnetic head is moved across a magnetic tape to read data on the longitudinal tracks of said magnetic tape, .[.the.]. .Iadd.a .Iaddend.method of presetting said magnetic head to a reference track on .[.tapes.]. .Iadd.a tape .Iaddend.written in .[.both standard and non-standard formats.]. .Iadd.either a first format or an other format, said first format having load zone and data zone portions and reference bursts in longitudinal tracks in said load zone, said other format having data zone portions but having no such reference bursts in a portion corresponding to the load zone portion of said first format, said method .Iaddend.comprising: reading a .Iadd.portion of said tape corresponding to the .Iaddend.load zone portion of said .[.tape.]. .Iadd.first format.Iaddend.;   determining whether said tape is written in said .[.standard.]. .Iadd.first .Iaddend.or .[.a non-standard.]. .Iadd.said other .Iaddend.format from .[.the.]. data read in said zone .[.;.]. .Iadd.portion corresponding to the .Iaddend.load .Iadd.portion of said first format, and performing the following additional steps if the determined format is said other format: .Iaddend.   moving said head .[.to.]. .Iadd.over .Iaddend.successive .Iadd.longitudinal .Iaddend.tracks toward .[.the.]. .Iadd.one lateral .Iaddend.edge of said tape .[.if the determined format is non-standard.].;   .[.reading data.]. .Iadd.detecting whether data is present .Iaddend.in the data zones of said successive .Iadd.longitudinal .Iaddend.tracks including detecting whether data is present in fixed intervals of reading;   identifying the .Iadd.location of said one lateral .Iaddend.edge of said tape when .[.no.]. data is .[.read.]. .Iadd.no longer detected.Iaddend.; and   moving said head a .[.known.]. .Iadd.predetermined .Iaddend.distance from the .[.edge of said tape.]. .Iadd.identified location .Iaddend.to .[.said.]. .Iadd.the .Iaddend.reference track .Iadd.of said other format.Iaddend.;   said magnetic tape drive being in combination with a controller and a host computer wherein said tape drive is connected through an interface to .[.a.]. .Iadd.the .Iaddend.controller and host computer, and wherein said host computer generates a REPORT DRIVE CONFIGURATION command applied to said drive through said interface, and wherein said drive thereafter generates a NON-STANDARD MODE status to said controller through said interface.   
     
     
       16. In a magnetic tape drive of the type in which a magnetic head is moved across a magnetic tape to read data on longitudinal tracks of said magnetic tape and wherein said .[.tapes are.]. .Iadd.magnetic tape is .Iaddend.written in .[.both standard and non-standard formats.]. .Iadd.either a first format or an other format.Iaddend., wherein said .[.standard.]. .Iadd.first .Iaddend.format .[.tape.]. is written in segments of data along each of said tracks, wherein there are relatively large blank gaps between said segments and wherein an index pulse is generated at the end of each gap signifying the start of each data segment, .[.a method of reading data from non-standard tapes which have.]. .Iadd.and further wherein said other format has .Iaddend.relatively small blank gaps between data segments and irrelevant data in a remaining portion .[.of the track.]. between the data segments .Iadd.of each of said longitudinal tracks, a method of reading data from said tape .Iaddend.comprising: determining whether said tape is written in said .[.standard or non-standard format from the data read in a load zone.]. .Iadd.first format or said other format.Iaddend., and in response to a determination .[.of a non-standard.]. .Iadd.that said tape is written in said other .Iaddend.format, performing the following steps .[.;.]. .Iadd.: .Iaddend.   detecting said relatively small blank gaps;   timing out a remainder of a time interval between data segments in response to said detection; and   generating an index pulse at the end of the timing out, said index pulse being supplied to an interface of said tape drive.   
     
     
       17. The method recited in claim 16 wherein said irrelevant data is servo information having data transitions. 
     
     
       18. The method recited in claim .[.16.]. .Iadd.17 .Iaddend.wherein the step of timing out the remainder of the time interval between data segments comprises: counting data transitions in said servo information; and   enabling the generation of said index pulse after a predetermined number of .[.such.]. .Iadd.said data .Iaddend.transitions have occurred.   
     
     
       19. The method recited in claim 16 wherein the tape drive is connected to a controller by an interface which transmits a SKIP command to the tape drive specifying movement of .Iadd.the .Iaddend.tape by a specified number of data segments in the forward or reverse .[.directions.]. .Iadd.direction.Iaddend., said method further comprising performing .[.a.]. .Iadd.the .Iaddend.SKIP command on a .[.non-standard.]. tape .Iadd.having said other format .Iaddend.by the steps of: counting said small blank gaps during performance of .[.a.]. .Iadd.the .Iaddend.SKIP command; and   exiting the performance of said SKIP command when the count equals said specified number of data segments.   
     
     
       20. A magnetic tape drive for digital computer backup of the type in which a magnetic head is moved across a magnetic tape to read digital data on longitudinal tracks between the .Iadd.lateral .Iaddend.edges of said magnetic tape, .[.said longitudinal tracks having load zone and date zone portions.]. and wherein said magnetic head is preset to a reference track on tapes written in .[.both standard and non-standard formats.]. .Iadd.either a first format or an other format, said first format having load zone and data zone portions and reference bursts in longitudinal tracks in said load zone, said other format having data zone portions but having no such reference bursts in a portion corresponding to the load zone portion of said first format, said method .Iaddend.comprising: means for reading a .Iadd.portion of a tape corresponding to the .Iaddend.load zone portion of said .[.tape.]. .Iadd.first format.Iaddend.;   means for determining .Iadd.from data read in said portion corresponding to the load zone portion of said first format .Iaddend.whether .[.the format of said data in a load zone portion of.]. said tape is written in said .[.standard.]. .Iadd.first format .Iaddend.or .[.a non-standard.]. .Iadd.said other .Iaddend.format;   means for moving said head .[.to.]. .Iadd.across .Iaddend.successive tracks toward .[.an.]. .Iadd.one lateral .Iaddend.edge of said tape if the determined format is .[.non-standard.]. .Iadd.said other format.Iaddend.;   means for .[.reading data.]. .Iadd.detecting whether data is present .Iaddend.in the data zone portions of said successive .Iadd.longitudinal .Iaddend.tracks .Iadd.as said head moves toward said one lateral .Iaddend.edge of said tape;   means for identifying the .Iadd.location of said one lateral .Iaddend.edge of said tape when .[.no.]. data is .[.read.]. .Iadd.no longer detected.Iaddend.; and   means for moving said head a .[.known.]. .Iadd.predetermined .Iaddend.distance from the .Iadd.identified location of said one lateral .Iaddend.edge of said tape to .[.said.]. .Iadd.the .Iaddend.reference track .Iadd.of said tape.Iaddend..   
     
     
       21. The tape drive recited in claim 20 wherein magnetic tapes written in said .[.standard.]. .Iadd.first .Iaddend.format have reference bursts in said load zone portions of said tracks and wherein the means for determining whether said tape is written in said .[.standard.]. .Iadd.first format .Iaddend.or .[.non-standard.]. .Iadd.said other .Iaddend.format comprises: means for searching for said reference bursts in .Iadd.the portion of said tape corresponding to .Iaddend.said load zone .Iadd.portion of said first format.Iaddend.; and   means for providing an indication that said tape is written in .[.a non-standard.]. .Iadd.said other .Iaddend.format if .[.no such.]. .Iadd.said .Iaddend.reference bursts are .Iadd.not .Iaddend.detected.   
     
     
       22. The tape drive recited in claim 21 further comprising: means for moving said tape through said load zone .Iadd.portion .Iaddend.into said data zone .Iadd.portion .Iaddend.before .[.data.]. .Iadd.detecting whether data is present .Iaddend.in .Iadd.said .Iaddend.successive .Iadd.longitudinal .Iaddend.tracks .[.is read.]..   
     
     
       23. The tape drive recited in claim 20 further comprising: a stepper motor for moving said head is incremental steps across said tape.   
     
     
       24. The tape drive recited in claim 23 wherein said head is moved a .[.known.]. .Iadd.pre-determined .Iaddend.distance from the .Iadd.identified location of said one lateral .Iaddend.edge of the tape by actuating said stepper motor a fixed number of times to move said head a fixed number of incremental steps. 
     
     
       25. The tape drive recited in claim 20 in combination with a controller and a host computer, said tape drive being connected through an interface to said controller.[.;.]..Iadd., said combination further comprising: .Iaddend. means in said host computer for generating a REPORT DRIVE CONFIGURATION command .Iadd.that is .Iaddend.applied to said drive through said interface; and   means in said drive for generating a NON-STANDARD MODE status to said controller through said interface in response to a determination that said tape is written in said .[.non-standard.]. .Iadd.other .Iaddend.format.   
     
     
       26. The magnetic tape drive recited in claim 20 wherein said .[.standard.]. .Iadd.first .Iaddend.format .[.tape.]. is written in segments of data along each of said tracks, wherein there are relatively large blank gaps between said segments, wherein an index pulse is generated at the end of each gap signifying the start of each data segment, and wherein said .[.non-standard tapes have.]. .Iadd.other format has .Iaddend.relatively small blank gaps between data segments and irrelevant data in a remaining portion .[.of a track.]. between the data segments .Iadd.of said longitudinal tracks.Iaddend., said tape drive further comprising: means for detecting said relatively small blank gaps;   means for timing out a remainder of time in said blank gaps between data segments in response to said detection; and   means for generating an artificial index pulse at the end of the timing out, said index pulse being supplied to an interface of said tape drive.   
     
     
       27. The tape drive recited in claim 26 .Iadd.wherein .Iaddend.the tape drive is connected to a controller by .[.an.]. .Iadd.said .Iaddend.interface which transmits a SKIP command to the tape drive specifying movement of .Iadd.the .Iaddend.tape by a specified number of data segments in the forward or reverse direction, said tape drive further comprising: means for performing .[.a.]. .Iadd.the .Iaddend.SKIP command on a .[.non-standard.]. tape .Iadd.having said other format .Iaddend.including:   means for counting said small blank gaps during performance of .[.a.]. .Iadd.the .Iaddend.SKIP command; and   means for exiting the performance of said SKIP command when the count equals said specified number of data segments.   
     
     
       28. The tape drive recited in claim 27 wherein said means for counting comprises: a counter, said counter being set with the specified number of data segments to be skipped, said counter being decremented each time a short duration gap is detected; and   wherein said means for exiting is responsive to the count in said counter means.   
     
     
       29. The tape drive recited in claim 26 .Iadd.wherein said tape is written in either said first format or one of a plurality of different types of other formats, .Iaddend.further comprising: means for determining the length of said data segments on .Iadd.a tape determined to be written in one of .Iaddend.said .[.non-standard tapes.]. .Iadd.other formats.Iaddend.; and   means for indicating the type of .[.non-standard.]. .Iadd.other format in which said .Iaddend.tape .Iadd.is written .Iaddend.based on the length of said data segments. .Iadd.30. The method recited in claim 1 wherein said first format is characterized by reference bursts in said load zone portion, and wherein said step of determining whether said tape is written in said first format, said other format, or is unformatted comprises:   providing an indication that said tape is written in said first format if reference bursts are detected in the load zone portion of said tape, but if no such reference bursts are detected, moving said tape so that said head reads the data zone portion of said tape; and   indicating that said tape is not formatted if no data is read in said data zone, but if data is read in said data zone, indicating that said tape is written in said other format. .Iaddend. .Iadd.31. The method recited in claim 7 wherein said step of moving said head a predetermined distance to the reference track of a tape having said other format comprises:   moving said head across successive tracks toward one lateral edge of said tape;   detecting whether data is present in the data zones of said successive tracks as said head moves toward said one lateral edge;   identifying the location of the lateral edge of said tape when data is no longer detected; and   moving said head a predetermined distance from the identified location of said one lateral edge of said tape to the reference track. .Iaddend.   
     
     
        .Iadd.2.  In a magnetic tape drive of the type in which a magnetic head is moved across a magnetic tape to read data on longitudinal tracks between the lateral edges of said magnetic tape, a method of determining whether a tape is written in a first format or an other format or is unformatted, said first format having a load zone portion and a data zone portion and reference bursts in longitudinal tracks in said load zone portion, said other format having a data zone portion but having no such reference bursts in a portion corresponding to the load zone portion of said first format, said method comprising: reading a portion of said tape corresponding to the load zone portion of said first format;   providing an indication that said tape is written in said first format if reference bursts are detected when reading said portion corresponding to the load zone portion of said first format, but if no reference bursts are detected, moving said tape so that said head reads the data zone portion of said tape; and   indicating that said tape is not formatted if no data is read in said data zone, but if data is read in said data zone, indicating that said tape is written in said other format..Iaddend. .Iadd.33. The method recited in claim 32 wherein if the format of said tape is determined to be said other format, the following additional steps are performed:   moving said head across successive tracks toward one lateral edge of said tape;   detecting whether data is present in the data zone portions of said successive longitudinal tracks as said head moves toward said one lateral edge of said tape;   identifying the location of the lateral edge of said tape when data is no longer detected; and   moving said head a predetermined distance from the lateral edge of said   
     
     
        tape to the reference track of said other format..Iaddend. .Iadd.34.  The method recited in any one of claims 1, 7, 8, 12, 15, 16, or 32, wherein said first format comprises a QIC format, and wherein said other format comprises an Irwin format..Iaddend. .Iadd.35. The magnetic tape drive recited in claim 20 wherein said first format comprises a QIC format, and wherein said other format comprises an Irwin format..Iaddend.