The simple disk controller is not used by CPM or Versados, but exists anyway. It is an Emulator Only device.

Located at $F1A300 thru $F1A31f  (unused locations return 0)
these are illegal in real VME10

'   CmdSts-H     CmdSts-L     +00
'   Drive-H      Drive-L      +02
'   Cylinder-H   Cylinder-L   +04
'   Head-H       Head-L       +06
'   Sector-H     Sector-L     +08
'   DMA-hh       DMA-hl       +0a
'   DMA-lh       DMA-ll       +0c

'   Cylinders/Disk   H and L     +14h
'   Heads/disk       H and L     +16h
'   Sector/track     H and L     +18h
'   Sector Size      H and L     +1ah

if a disk's sector size is 256, reads 256 bytes...no auto-de-blocking

WARNING
 each time a read or write occurs, 
 the IO Buffer is RE-DIMed to the size of the sectors on the curent track 
  This means that the DMA transfer is to/from a buffer of that size... 
 you must ensure that the IO buffer used in software is at least as big as the 
   largest sector that you will access on the drive...

Must access registers as words or longwords, not byte

Must write C H S in order (sector must be last for IMD files to scan for sector correctly)


Reading Status clears the status, so must read status to clear errors from previous IO


read status
(select drive)
(set C H S)
(set DMA)
write command
read status

at any time, can read status, but clears errors 
	so if error, do NOT continue
Commands are 

	Read = 1

	Write = 2

Status word is ...

' 15 14 13 12 11 10 9  8  7   6   5   4   3   2   1   0
'                        R/W  WP DMA  C   H   S  DRV CMD

note---for IMD files compressed data is expanded for read... not allowed to write to disk with compressed sectors or bad sectors

deleted address marks are not handled right. Nor are sectors with errors.

