Commodore 1541-II - Appendix A: Changing Device Number; Software and Hardware Methods

APPENDIX B: DOS ERROR MESSAGES AND LIKELY CAUSES
Note: Many commercial program diskettes are intentionally created with one or
more of the following errors, to keep programs from being improperly duplicated.
If a disk error occurs while you are making a security copy of a commercial
program diskette, check the program's manual. If its copyright statement does not
permit purchasers to copy the program for their own use, you may not be able to
duplicate the diskette. In some such cases, a safety spare copy of the program
diskette is available from your dealer or directly from the company for a reasonable
fee.
00: OK (not an error)
This is the message that usually appears when the error channel is checked. It
means there is no current error in the disk unit.
01: . FILES SCRATCHED (not an error)
This is the message that appears when the error channel is checked after using the
Scratch command. The track number tells how many files were erased.
NOTE: If any other error message numbers less than 20 ever appear, they may be
ignored. All true errors have numbers of 20 or more.
20: READ ERROR (block header not found)
The disk controller is unable to locate the header of the requested data block.
Caused by an illegal block, or a header that has been destroyed. Usually
unrecoverable.
21: READ ERROR (no sync character)
The disk controller is unable to detect a sync mark on the desired track.
Caused by misalignment, or a diskette that is absent, unformatted or
improperly seated. Can also indicate hardware failure. Unless caused by one
of the above simple causes, this error is usually unrecoverable.
22: READ ERROR (data block not present)
The disk controller has been requested to read or verify a data block that was not
properly written. Occurs in conjunction with Block commands and indicates an
illegal track and/or sector request.
23: READ ERROR (checksum error in data block)
There is an error in the data. The sector has been read into disk memory, but its
checksum is wrong. May indicate grounding problems. This fairly minor error is
often repairable by simply reading and rewriting the sector with direct access
commands.
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