0010             DDI2 has two standard entry points:
 0020   
 0030  DESELECT   ($9A03)
 0040             DESELECT will intrepret the control code in IFLAGS. If you want
 0050  to         trun off the drive(s), you should store 00 in IFLAGS and then call
 0060  DESELECT.
 0070   
 0080   
 0090  DISKIO     ($9A00)
 0100             The value in accumulator is the command code. Valid command codes
 0110  are        0 to 6 and 8. The functions of each command are:
 0120   
 0130  0:         initialization
 0140             Determine the drive size and initialize IRQ vector.
 0150  1:         restore the drive and set diskette parameters.
 0160             i.e. find the density,sector length,sectors per track.
 0170  2:         restore the drive only.
 0180  3:         seek track, track number in ITRACKS.
 0190  4:         read sector, track number in ITRACKS, secotr number in ISECTR,
 0200             transfer address in IADDRS (2 bytes).
 0210  5:         write sector, others same as 4.
 0220  6:         user define function. Jump to $a614 when invoked.
 0230             It is used by FORMAT and FMT&CPY to do track formatting.
 0240  8:         read the 2nd to 8th byte oID sector if 1st byte is IDMARK.
 0250             The data is stored at $A609-$A610.
 0260   
 0270  All        commands return with carry set if error occurs and error code is
 0280  stored     in accumulator.
 0290   
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