Commodore 1541 - Description of Dos Error Messages

DESCRIPTION OF DOS ERROR MESSAGES
NOTE: Error message numbers less lhan 20 should be ignored with the exception of 01
which gives information about the number of Tiles scratched with the SCRATCH com
mand.
20- READ ERROR (block header not found)
The disk controUer is unable to locate the header of the requested data block.
Caused by an illegal block number, or the header has been destroyed.
21: READ ERROR (no sync character)
The disk controller is unable to detect a sync mark on the desired track. Caused
by misalignment of the read/writer head, no diskette is present, or unformatted
or improperly seated diskette. Can also indicate a hardware failure.
22: READ ERROR (data block not present)
The disk controUer has been requested to read or verify a data block that was
not properly written. This error message occurs in conjunction with the BLOCK
commands and indicates an illegal track and/or block request.
23: READ ERROR (checksum error in data block)
This error message indicates that there is an error in one or more of the data
bytes. The data has been read into the DOS memory, but the checksum over the
data is in error. This message may also indicate grounding problems.
24- READ ERROR (byte decoding error)
The data or header as been read into the DOS memory, but a hardware error has
been created due to an invalid bit pattern in the data byte. This message may also
indicate grounding problems.
25: WRITE ERROR (write-verify error)
This message is generated if the controller detects a mismatch between the writ
ten dala and the data in the DOS memory.
26: WRITE PROTECT ON
This message is generated when the controller has been requested to write a dala
block while the write protect switch is depressed. Typically, this is caused by us
ing a diskette with a write a protect tab over the notch.
27- READ ERROR (checksum error in header)
The controller has detected an error in the header of the requested data block.
The block has not been read into the DOS memory. This message may also in
dicate grounding problems.
28: WRITE ERROR (long data block)
The controller attempts to detect the sync mark of the next header after writing a
data block. If the sync mark does not appear within a pre-delermined time, the
error message is generated. The error is caused by a bad diskette format (the
data extends into the next block), or by hardware failure.
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