03F0-03F7 ---- FDC 1  (1st Floppy Disk Controller 8272)  same as 0370


03F0       diskette controller status A (PS/2)
        bit 7   interrupt pending
        bit 6   second drive installed
        bit 5   step
        bit 4   track 0
        bit 3   head 1 select
        bit 2   index
        bit 1   write protect
        bit 0   direction

03F1   r   diskette controller status B (PS/2)
        bit 7-6  reserved
        bit 5    drive select (0=A:, 1=B:)
        bit 4    write data
        bit 3    read data
        bit 2    write enable
        bit 1    motor enable 1
        bit 0    motor enable 0

03F2   w   diskette controller DOR (Digital Output Register)
        bit 7-6    reserved PS/2
        bit 7 = 1  drive 3 motor enable
        bit 6 = 1  drive 2 motor enable
        bit 5 = 1  drive 1 motor enable
        bit 4 = 1  drive 0 motor enable
        bit 3 = 1  diskette DMA enable (reserved PS/2)
        bit 2 = 1  FDC enable  (controller reset)
              = 0  hold FDC at reset
        bit 1-0    drive select (0=A 1=B ..)

03F4   r   diskette controller status register
        bit 7 = 1  data register is ready
        bit 6 = 1  transfer is from controller to system
            0  transfer is from system to controller
        bit 5 = 1  non-DMA mode
        bit 4 = 1  diskette controller busy
        bit 3 = 1  drive 3 busy (reserved on PS/2)
        bit 2 = 1  drive 2 busy (reserved on PS/2)
        bit 1 = 1  drive 1 busy
        bit 0 = 1  drive 0 busy

03F5   r   diskette command status register 0
        bit 7-6      last command status
            = 00  command terminated successfully
            = 01  command terminated abnormally
            = 10  invalid command
            = 11  terminated abnormally by change in ready signal
        bit 5   = 1   seek completed
        bit 4   = 1  equipment check occurred after error
        bit 3   = 1  not ready
        bit 2   = 1  head number at interrupt
        bit 1-0 = 1  unit select (0=A 1=B .. )
                 (on PS/2  01=A  10=B)

       status register 1
        bit 7      end of cylinder; sector# greater then sectors/track
        bit 6 = 0
        bit 5 = 1  CRC error in ID or data field
        bit 4 = 1  overrun
        bit 3 = 0
        bit 2 = 1  sector ID not found
        bit 1 = 1  write protect detected during write
        bit 0 = 1  ID address mark not found

       status register 2
        bit 7 = 0
        bit 6 = 1  deleted Data Eddress Mark detected
        bit 5 = 1  CRC error in data
        bit 4 = 1  wrong cylinder detected
        bit 3 = 1  scan command equal condition satisfied
        bit 2 = 1  scan command failed, sector not found
        bit 1 = 1  bad cylinder, ID not found
        bit 0 = 1  missing Data Address Mark

       status register 3
        bit 7      fault status signal
        bit 6      write protect status
        bit 5      ready status
        bit 4      track zero status
        bit 3      two sided status signal
        bit 2      side select (head select)
        bit 1-0    unit select (0=A 1=B .. )

03F6   r/w FIXED disk controller data register
        bit 7-4    reserved
        bit 3 = 0  reduce write current
            1  head select 3 enable
        bit 2 = 1  disk reset enable
            0  disk reset disable
        bit 1 = 0  disk initialization enable
            1  disk initialization disable
        bit 0      reserved

03F7   r   diskette controller DIR (Digital Input Register)
        bit 7 = 1 diskette change

        bit 6     FIXED DISK write gate
        bit 5     FIXED DISK head select 3 / reduced write current
        bit 4     FIXED DISK head select 2
        bit 3     FIXED DISK head select 1
        bit 2     FIXED DISK head select 0
        bit 1     FIXED DISK drive 1 select
        bit 0     FIXED DISK drive 0 select   conflicts with:

        bit 0     diskette high density select

03F7   w   select register for diskette data transfer rate
        bit 7-2       reserved
        bit 1-0 = 00  500 Kb/S mode
            = 01  300 Kb/S mode
            = 10  250 Kb/S mode
            = 11  reserved