US 5373485

US Patent 5373485, titled "Method for locating data in a data cartridge system," was issued on December 13, 1994, from an application filed on September 3, 1991. [cite: The provided patent text] The patent was originally assigned to Minnesota Mining and Manufacturing Co, which is now listed as 3M Co. [cite: The provided patent text] The inventors are Michael A. Hogan, George W. Blattner, Charles R. Kummeth, and Alan R. Olson. [cite: The provided patent text]

Abstract:
The patent describes a method and apparatus for locating data, including physical blocks, logical blocks, and the end of data, on a data tape written in a serpentine pattern. The physical block search decodes a physical address to determine the track location and physical block address on the serpentine tape. The tape is manipulated bidirectionally, and the algorithm leverages the serpentine nature and block locations to find the physical address. For logical blocks, a logical address is used to predict a target track number. This prediction is then iteratively refined until the logical block is found. The end of data is located using a binary search algorithm, utilizing knowledge of the serpentine data pattern's track assignment. [cite: The provided patent text]

Independent Claims Overview:

Independent Claim 1:
Claim 1 describes a method for locating the end of data on a serpentine-written tape. This method involves a series of steps employing a binary search approach:

• Initial Setup:
  • Defining a "difference in the number of tracks between end of data signals" by adding one to the number of tracks between those with end of data signals in their track headers. [cite: The provided patent text]
  • Setting a "low bound" to the lowest track number. [cite: The provided patent text]
  • Setting a "high bound" to the next higher power of two that is greater than or equal to the lowest track plus the difference between the highest and lowest track. [cite: The provided patent text]
• Iterative Search (Binary Search Logic):
  • Calculating a "target track" as an upper integer bound of the low track bound plus half the difference between the high and low track bounds. [cite: The provided patent text]
  • Comparing the target track to the highest track; if the target track is greater, the current track is set to the highest track; otherwise, the current track is set to the target track. [cite: The provided patent text]
  • Positioning the tape to the beginning of this current track. [cite: The provided patent text]
  • Checking for an "end of data" signal at the beginning of the current track. [cite: The provided patent text]
  • Evaluating conditions:
    • If the difference between the high bound and low bound is less than or equal to the "difference in the number of tracks between end of data signals," and an "end of data" signal is found at the beginning of the current track, then proceed to step (k). [cite: The provided patent text]
    • If the first part of the condition is true but no "end of data" signal is at the beginning of the current track, proceed to step (l). [cite: The provided patent text]
  • Adjusting the search bounds:
    • If no "end of data" signal is at the beginning of the current track (meaning data is present), the low track bound is set to the target track. [cite: The provided patent text]
    • If an "end of data" signal is at the beginning of the current track (meaning no data), the high track bound is set to the target track. [cite: The provided patent text]
  • Returning to the initial track difference setting step (a) for further iteration. [cite: The provided patent text]
• Final Data Location:
  • If the condition in (h) leads to step (k): The current track is reset to the current track minus the "difference in the number of tracks between end of the data signals." [cite: The provided patent text]
  • Positioning the tape to the beginning of this (potentially adjusted) current track. [cite: The provided patent text]
  • Scanning the tape from that position until the "end of the data" signal is found. [cite: The provided patent text]

CAFC 2026 Dockets:
As of April 26, 2026, no authoritative information regarding US patent 5373485 was found in the CAFC 2026 dockets. Case records for patents filed before March 1, 2012, are typically stored with the National Archives and Records Administration, requiring specific requests for access rather than direct docket searches.