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Programmable Track Correction for Tapes

IP.com Disclosure Number: IPCOM000094632D
Original Publication Date: 1965-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Beausoleil, WF: AUTHOR [+4]

Abstract

The computer system permits changing the course of system operation whenever any reading tape drive detects an error. This permits the system to take up any next occurring instruction, including selection of another tape drive on the same tape control. The program can then later return to the erroneous tape drive and correct its previously read erroneous information.

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Programmable Track Correction for Tapes

The computer system permits changing the course of system operation whenever any reading tape drive detects an error. This permits the system to take up any next occurring instruction, including selection of another tape drive on the same tape control. The program can then later return to the erroneous tape drive and correct its previously read erroneous information.

A Track-In-Error (TIE) register is in the tape control for indicating which tape track has one or more erroneous bits in an erroneously read tape data block. A one bit in any of TIE register positions 0...7 indicates that an error exists in the corresponding track 0...7 of the last read tape block of that tape drive, which has an address indicated by a tape drive select register in the tape control. The determination of which track is in error is done by devices, not shown.

After reading each block of tape data found to have an error, a branch is made to a sense instruction. This causes a plurality of sense bytes to be transmitted to main memory under program control by the system control, as is usually done. However, an additional sense byte is provided to transmit the TIE information from the TIE register to the prescribed address - X in main memory. Address X is specified either by the computer program or it can be a fixed address. The drawing shows an example of address X for storing an instruction having a TIE operation code. The TIE information is located in bit positions 0...7 of address X. Other bit positions contain the corresponding tape drive address. Alternatively, the TIE information can be put in a device table in main memory which stores the status of all I/O devices connected to the computer system for easy table lookup by a branch instruction in the main program.

After the...