Commodore Amiga A500 Technical Reference Manual page 188

To maximize data read back efficiency and maintain the interleave
factor of one, as closely as possible, it is required that the physical
sector numbers be offset by a sector from track t o track. (see table)
so that the HDC has a sector length available for overhead t o switch
heads while on the same cylinder.
Read Drive (Class 0,
Action
Opcode 8)
Read the specified number of consecutive sectors beginning with the
specified sector in the command block t o the host computer. If ECC
is enabled, ECC bytes are recomputed by the HDC. After the data is
transferred t o the host, the recorded ECC bytes are compared to the
generated bytes to generate the syndrome bytes. If the syndrome is
non-zero, errors have occurred. Error correction is invoked by the
HDC
if
two consecutive syndromes match, otherwise a maximum of
8 retries are attempted by the HDC.
Possible Error Codes
No error, invalid command, invalid sector address, invalid LUN, IDNF
error, bad block mark, address mark not found, uncorrectable data
error, write fault, drive not ready, seek in progress, DMA error.
Write Drive (Class 0,
Action
Opcode A)
The Write Sector command is used t o write the specified number of
sectors of data from the host computer to the disk, beginning with
the specified logical address in the command block. The write oper-
ation is identical to the read, except for error handling and reading
the host status.
Possible Error Codes
No error, invalid command, invalid sector address, invalid LUN, drive
not ready, IDNF error, bad block mark, write fault, seek in progress,
DMA error.
Seek (Class
0, Opcode B)
Action
The Seek command positions the R N head t o the cylinder contained
in the logical address. No ID field is read t o verify start or end posi-
tion. Seek It is primarily used t o move the R N head t o the Shipping
zone for transportation of the hard disk.
Possible Error Codes