On Monday 18 December 2000 13:41, you wrote:

> Someone have information on the Turbo-R FDC? (including a datasheet)

The info below is from Henrik Gilvad. He wanted to publish it on a disk 
magazine, but I'm not sure it ever was. Anyway, I don't think he will mind me 
posting it here.

Bye,
		Maarten

===========================================================================

Turbo R Floppy Disk Controller informations. Written by Henrik Gilvad.
----------------------------------------------------------------------
The Turbo R FDC is in the chip called "TC8566AF" from Toshiba. This chip is
compatible with the "PD765" from NEC. The PD765 have been used in IBM PC's and
in some homecomputers like the Schneider models. Most of NEC's newer FDC's are
also register compatible with the "PD765" (like the newer "PD72068").

The FDC actually have its registers spread over 16 locations. The S1990 chip 
activates the FDC on any location between #7FF2-#7FFB, the S1990 use the rest.

#7FF0   Mapper page used for DOS 2 and diskbasic.
        00 : DOS2 page 0
        01 : DOS2 page 1
        02 : DOS2 page 2
        03 : Diskbasic
        04-07: Other rompages which are not used for Floppy purposes.

#7FF1 R DiskChange & HighDensity detect port.
        bit 0   FD2HD1  High Density detect drive 1 (TP38 on the PCB)
        bit 1   FD2HD2  ------------------------- 2 (TP37 on the PCB)
        bit 4   FDCHG1  Disk Change detect on drive 1 (Not on original drive)
        bit 5   FDCHG2  --------------------------- 2
        The bits are active low. Other bits are always '0' so you will
        normally read #33 from this port.

#7FF2 W Motor + LED port.
        7   6   5   4   3   2   1  0
        |   |   |   |   |   |   +--+--- Drive select. 0-3 (A-D)
        |   |   |   |   |   +---------- (0) Reset FDC. (1) Enable FDC
        |   |   |   |   +-------------- (1) Enable DMA and Interrupt.
        |   |   |   |                   (Always =0 on Turbo R !)
        |   |   |   +------------------ Motor Select Drive A. (1=on, 0=off)
        |   |   +---------------------- --------!!-------- B
        |   +-------------------------- --------!!-------- C
        +------------------------------ --------!!-------- D
        #14 for Drive 0
        #25 for Drive 1
        Write #00 to stop both drives and RESET FDC.
        Write #04 to stop both drives but keep FDC enabled.

#7FF3   ? Some routines writes this sequence to it. [2,3,2]
        Some writes #20 or #30 to it.

#7FF4   FDC status (R) (Just some guesses because I don't have the datasheets)
        7   6   5   4   3   2   1   0
        |   |   |   |   |   |   |   +-- (1) Drive 0 in Seek mode
        |   |   |   |   |   |   +------ (1) ----- 1 in Seek mode
        |   |   |   |   |   +---------- (1) ----- 2 in Seek mode (not on TBR)
        |   |   |   |   +-------------- (1) ----- 3 in Seek mode (not on TBR)
        |   |   |   +------------------ (1) FDC Busy. Read or Write command
        |   |   |                           is in process.
        |   |   +---------------------- (1) Non-DMA Mode. CPU polled transfer.
        |   +-------------------------- Data (1) To CPU. (0) To FDC.
        +------------------------------ Request for Master.
                                        (1) Data register is ready to send or
                                            receive data.
        Auxilary Command port (W)

#7FF5   FDC data port (R/W)
        Used for all data in Command, Execution and Result Phase.
#7FF6   ? (Not used ?)
#7FF7   Control register (W).
        00h = FDC can only read/write 1.44Mbyte disks.
        01h = FDC can only read/write 720kbyte disks.
        After a reset the FDC defaults to the normal 720K disks.
#7FF8-#7FFB ?

The last 4 addresses are not FDC registers and they does not seems to be used 
in any ROM's.

#7FFC   ? bit 0 can be read and written. bit 1 is always 0.
#7FFD   ? bit 0-1 can be read and written.
#7FFE   ? always #FF ?
#7FFF   ? always #3F ?


The FDC have 15 Commands. There are 3 Phases in all commands, they are:

        COMMAND PHASE
        The FDC receives the 'Command Block' from the CPU.

        EXECUTION PHASE
        The FDC performs the operation it was instructed to do.
        This includes transfer of Sector Data etc.

        RESULT PHASE
        When the operation is finished the CPU must read a 'Status Block'.
        When this block have been transfered then the FDC should be ready
        for a new Command, else something must be wrong with the previous
        communication. (Usually wrong Phase-Lengths) Then it might be
        nessesary to Reset the FDC and set it up again before the next
        command.


Command Summary:
----------------
Com.  Len.  Function            Data            Status   Note
-----------------------------------------------------------------------------
x0
x1      9   Scan Equal          ?               7
x2      9   Read a Track        All data.       7       In 1 rotation !
03      3   Specify             none            none    Sets timings
04      2   Sense Drive Status
x5      9   Write Sector        Sector(s)*Size  7
x6      9   Read Sector         Sector(s)*Size  7
x7      2   Recalibrate                         none    Goto Track 00
08      1   Sense Seek Status   none            2       (after Seek Commands)
x9      9   Write Deleted Data  ? (Size + 2 ?)  7
59      9   Scan Low or Equal   ?               7
xA      2   Read ID             4 bytes 'CHRN'  7
xB
xC      9   Read Deleted Data   ? (Size + 2 ?)  7
xD      6   Format Track        Sectors*'CHRN'  7
5D      9   Scan High or Equal  ?               7
xE
0F      3   Seek                none            none    Goto Track#.
-----------------------------------------------------------------------------
x0, xB and xE are illegal commands. (x means Flags in the upper 3 bits)


SYMBOL DESCRIPTIONS:
--------------------
C       Cylinder number. (=TRACK)
D       D stands for the data pattern that is going to be written into a
        sector
DTL     Data Length. When N is defined as 00, DTL stands for the data length
        that users are going to read from or write to the sector.
EOT     End Of Track. EOT stands for the final sector number on a cylinder.
GPL     Gap Length. GPL stands for the length of GAP3. (spacing between
        sectors excluding VCO sync field)
H       Head address. (0 or 1)
HD      Head. Head address stored in the 'CHRN' field on disk.
HLT     Head Load Time. Time from 4 to 512 ms. in 4.ms increments.
HUT     Head Unload Time. Time from 0 to 480 ms in 32 ms increments.
MF      FM or MFM mode. We use MFM on MSX. (Therefore MF always = 1 !!!)
MT      Multi-Track. If MT is high, a multi-track operation is to be performed
        (A cylinder under both HD0 and HD1 will be read or written.)
N       Number. N stands for the number of data bytes written in a sector.
        0 = 128, 1 = 256, 2 = 512, 3 = 1024 bytes/sector.
NCN     New Cylinder Number.
ND      Non-DMA Mode. ND=1 because we don't have DMA on MSX.
PCN     Present Cylinder Number. Stands for cylinder number at the completion
        of sense-interrupt status command indicating the position of the head
        at present time.
R       Record. R stands for the Sector number, which will be read or written.
R/W     Read/Write. R/W stands for either read (R) or write (W) signal.
SC      Sector. SC indicates the number of sectors per cylinder.
SK      Skip. SK stands for 'skip deleted-data address mark.'
SRT     Step Rate Time. SRT stands for stepping rate for the Drive.
        2 to 32 ms. in 2 ms increments.
ST0     Status byte 0
ST1     Status byte 1
ST2     Status byte 2
ST3     Status byte 3
STP     Scan Test. During a SCAN operation, if STP=1, the data in contiguous
        sectors is compared byte-by-byte with data sent from the CPU, and if
        STP=2, then alternate sectors are read and compared.
US0=US1 Unit Select. Binary number for DRIVE 0-3.


COMMANDS DETAILED
-----------------

+----------+
|Scan Equal|?
+----------+---+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W | MT  MF  SK   1   0   0   0   1 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               STP              |Scan Test                  |
+----------+---+--------------------------------+---------------------------+
|Execution      Data compared between the FDC and the CPU. (???)            |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+


+------------+
|Read a Track|Reads all sectors on track, as the sectors passes by.
+----------+-+-+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W |  0  MF  SK   0   0   0   1   0 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               DTL              |DaTaLength                 |
+----------+---+--------------------------------+---------------------------+
|Execution | R |CPU reads all data between Index hole and EOT               |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+
Note: Only DATA in the Sectors are transferred !
Note2:If interleave is 1/6/2/7/3/8/4/9/5 or other different from 1-9 then the
      sectors will be read in that order. (1 rotation)
      It gives faster copy on non '1-9' interleaves but is more difficult if
      errors occur.

+----------+
|Specify   |Set timings etc.
+----------+---+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+----------------+---------------+---------------------------+
|Command   | W |  0   0   0   0 | 0   0   1   1 |Command Codes              |
|          | W |  STEP RATE TIME|Head UnloadTime|SRT:2-32ms. HUT 0-480ms.   |
|          | W |  Head Load Time            | ND|ND:1=Non Dma. HLT:4-512    |
+----------+---+----------------------------+---+---------------------------+
|Execution      No data                                                     |
+---------------------------------------------------------------------------+
|Result         No result                                                   |
+---------------------------------------------------------------------------+
Note: Use #03,#DF,#03 on Turbo R.

+------------------+
|Sense Drive Status|Write Protected ?. And more flags.
+----------+---+---+----------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W |  0   0   0   0   0   1   0   0 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
+----------+---+--------------------------------+---------------------------+
|Execution      No data                                                     |
+----------+---+--------------------------------+---------------------------+
|Result    | R |    Status byte 3               | Status about Floppy Drive |
+----------+---+--------------------------------+---------------------------+


+------------+
|Write Sector|Writes 1 or more sectors.
+----------+-+-+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W | MT  MF   0   0   0   1   0   1 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               DTL              |DaTaLength                 |
+----------+---+--------------------------------+---------------------------+
|Execution | W |CPU transfers new sector data   |                           |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+


+------------+
|Read Sector |Reads 1 or more sectors.
+----------+-+-+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W | MT  MF  SK   0   0   1   1   0 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               DTL              |DaTaLength                 |
+----------+---+--------------------------------+---------------------------+
|Execution | R |CPU reads all sector data       |                           |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+

+-----------+
|Recalibrate|Moves head to Track 00
+----------++--+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W |  0   0   0   0   0   1   1   1 |Command Codes              |
|          | W |  X   X   X   X   X   0  US1 US0|Drive 0-3                  |
+----------+---+--------------------------------+---------------------------+
|Execution      No data                                                     |
+---------------------------------------------------------------------------+
|Result         No result phase                                             |
+---------------------------------------------------------------------------+
After this command then bit 0 (drive 0),1 (drive 1),2 (drive 2) or 3 (drive 
3) 
will be set to indicate that the CPU should send a 'Senes Interrupt Status 
(08)' to see when the command is finished.

+----------------------+
|Sense Interrupt Status|(After SEEK commands)
+----------+---+-------+------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W |  0   0   0   0   1   0   0   0 |Command Codes              |
+----------+---+--------------------------------+---------------------------+
|Execution      No data                                                     |
+----------+---+------------------------------------------------------------+
|Result    | R |           ST0                  |Status Byte 0              |
|          | R |           PCN                  |Present Cylinder Number    |
+----------+---+------------------------------------------------------------+
Bit5 in ST0 is set to '1' when the SEEK operation have ended.
Bit6 is set to '1' if TRACK00 was not met during a certain amount of steps.
     This means that the drive is missing or defect.


+-------------------------+
|Write Sector Deleted Data|(It seems that the CPU must write 2 bytes extra?)
+----------+---+----------+---------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W | MT  MF   0   0   1   0   0   1 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               DTL              |DaTaLength                 |
+----------+---+--------------------------------+---------------------------+
|Execution | W |CPU transfers new sector data   |                           |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+


+------------------+
|Scan Low or Equal |'Data compared between the FDD and main system' ?
+----------+---+---+----------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W | MT  MF  SK   1   1   0   0   1 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               STP              |DaTaLength                 |
+----------+---+--------------------------------+---------------------------+
|Execution | ? |'Data compared between thq FDD and main system' ?           |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+


+--------+
|Read ID |Read next 'CHRN' field
+--------+-+---+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W |  0  MF   0   0   1   0   1   0 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
+----------+---+--------------------------------+---------------------------+
|Execution |   |The first correct ID block is stored in the 'Result'        |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+
'CHRN' = Track, Head, Sector, Sector length.



+------------------------+
|Read Sector Deleted Data|(1 sector + 2 bytes extra ?)
+----------+---+---------+----------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W | MT  MF  SK   0   1   1   0   0 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               DTL              |DaTaLength                 |
+----------+---+--------------------------------+---------------------------+
|Execution | R |CPU reads sector data           |                           |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+



+-------------+
|Format Track |Formats all sectors on 1 Track/Side.
+----------+--++--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W |  0  MF   0   0   1   1   0   1 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                N               |Bytes/Sector (2=512)       |
|          | W |                SC              |Sectors/Track              |
|          | W |                GPL             |Gap 3 size                 |
|          | W |                D               |Fill sectordata with 'D'   |
+----------+---+--------------------------------+---------------------------+
|Execution | W |CPU transfers 'SC' * 'CHRN' data                            |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+
Execution data example: 00/00/01/02 00/00/02/02 00/00/03/02 00/00/04/02
                        00/00/05/02 00/00/06/02 00/00/07/02 00/00/08/02
                        00/00/09/02


+------------------+
|Scan High or Equal|'Data compared between the FDD and main system' ?
+----------+---+---+----------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W | MT  MF  SK   1   1   1   0   1 |Command Codes              |
|          | W |  X   X   X   X   X  Hd  US1 US0|Head 0/1, Drive 0-3        |
|          | W |                C               |Cylinder. (Track #)        |
|          | W |                H               |Head #                     |
|          | W |                R               |Record. (Sector# like 1-9) |
|          | W |                N               |Sector Size.0=128, 1=256.. |
|          | W |               EOT              |Last Sector # on Track     |
|          | W |               GPL              |GaP 3 Length.              |
|          | W |               STP              |DaTaLength                 |
+----------+---+--------------------------------+---------------------------+
|Execution | ? |'Data compared between the FDD and main system' ?           |
+----------+---+--------------------------------+---------------------------+
|Result    | R |               ST0              |Status Byte 0              |
|          | R |               ST1              |Status Byte 1              |
|          | R |               ST2              |Status Byte 2              |
|          | R |                C               |Cylinder after execution   |
|          | R |                H               |Head after execution       |
|          | R |                R               |Sector after execution     |
|          | R |                N               |SectorLength               |
+----------+---+--------------------------------+---------------------------+



+----------+
|Seek Track|Move head to Track#.
+----------+---+--------------------------------+---------------------------+
|Phase     |R/W| D7  D6  D5  D4  D3  D2  D1  D0 | Remarks                   |
+----------+---+--------------------------------+---------------------------+
|Command   | W |  0   0   0   0   1   1   1   1 |Command Codes              |
|          | W |  x   x   x   x   x  HD  US1 US0|Head0/1, Drive 0-3         |
|          | W |               NCN              |New Cylinder Number (Track)|
+----------+---+--------------------------------+---------------------------+
|Execution      No data                                                     |
+---------------------------------------------------------------------------+
|Result         No result phase                                             |
+---------------------------------------------------------------------------+
After this command then bit 0,1,2 or 3 will be set to indicate that the CPU
should send a 'Senes Interrupt Status (08)' to see when the movement is
finished.




COMMAND STATUS REGISTER's (Result Phase return data)
----------------------------------------------------

ST0
---
b7 b6 b5 b4 b3 b2 b1 b0
|  |  |  |  |  |  +--+- Unit Select. Drive Select 0-3
|  |  |  |  |  +------- Head Address. Head 0 or 1.
|  |  |  |  +---------- Not Ready.
|  |  |  |              Set if Drive goes 'Not Ready'
|  |  |  +------------- Equipment Check.
|  |  |                 Set if Track00 is not met with the "Recalibrate" CMD.
|  |  +---------------- Seek End. Set when the FDC completes the SEEK cmd.
+--+------------------- Interrupt code.
                        0 0 : Normal Termination of command.
                        0 1 : Abnormal Termination of command. (Not completed)
                        1 0 : Invalid command issue. (Never started)
                        1 1 : Abnormal Termination because the Drive's Ready
                              signal changed during command execution.


ST1
---
b7 b6 b5 b4 b3 b2 b1 b0
|  |  |  |  |  |  |  +- Missing Address Mark.
|  |  |  |  |  |  +---- Not Writable. (Due to Write Protect signal from drive)
|  |  |  |  |  +------- No Data. (1) if FDC cannot find specified sector.
|  |  |  |  |           (During ReadSector, WriteDeletedData or Scan commands)
|  |  |  |  +---------- 0
|  |  |  +------------- OverRun. (1) if the CPU did not read data fast enough.
|  |  +---------------- Data Error. (1) if FDC detects "CRC error"
|  +------------------- 0
+---------------------- End of cylinder. (1) if FDC tried to access a sector
                        beyond the final sector of a cylinder.

ST2
---
b7 b6 b5 b4 b3 b2 b1 b0
|  |  |  |  |  |  |  +- Missing Address Mark in data field
|  |  |  |  |  |  +---- Bad Cylinder. (Wrong Cylinder number)
|  |  |  |  |  +------- Scan Not Satisfied. If a SCAN cmd cannot find a sector
|  |  |  |  +---------- Scan Equal Hit. Set if the SCAN condition was met.
|  |  |  +------------- Wrong Cylinder. Set when Cylinder# is wrong.
|  |  +---------------- Data Error in Data Field. (1) when CRC error in data.
|  +------------------- Control Mark. (1) if 'Deleted Data Adr.Mark' was found
+---------------------- 0


ST3
---
b7 b6 b5 b4 b3 b2 b1 b0
|  |  |  |  |  |  +--+- Unit select 0-3
|  |  |  |  |  +------- Head Address
|  |  |  |  +---------- Two Side. Status from TwoSide signal from drive.
|  |  |  |              (Always '0' on Turbo R ?)
|  |  |  +------------- Track0. Status from current drive TRK00 detector.
|  |  +---------------- Ready. Status from current drive Ready.
|  +------------------- Write Protected. (1) when disk is writeprotected.
+---------------------- Fault. Status from Fault Signal from drive.
                        (Always '0' on Turbo R ?)





The Turbo R Diskbios have a workspace area. The base of this is stored at 
(#FD09 + PS * 16 + SS * 4 + 1) (Word)
IX is used to point to this area.

IX+00h  -  IX+09H ?

IX + 0Ah Command Block byte 1
IX + 0Bh ------------------ 2
IX + 0Ch ------------------ 3
IX + 0Dh ------------------ 4
IX + 0Eh ------------------ 5
IX + 0Fh ------------------ 6
IX + 10h ------------------ 7
IX + 11h ------------------ 8
IX + 12h ------------------ 9

IX + 13h used to store Status block byte 1
IX + 14h ------------------------------- 2
IX + 15h ------------------------------- 3
IX + 16h ------------------------------- 4
IX + 17h ------------------------------- 5
IX + 18h ------------------------------- 6
IX + 19h ------------------------------- 7



In DOS 2 I have found these routines in the DiskRom page 0:

#7824   The FORMAT TEXT
#785D   SCF:RET
#785F   LD A,#20:JR #786D
#7863   LD A,#30:JR #786D
#7867   LD A,#04                ;Motor Off, FDC (still) on.
        LD (#7FF2),A
        RET
#786D   LD (#7FF3),A            ;? I don't know the function of this port.
        RET
#7871   A routine to read a sector. (A Verify sector routine ?)
        The Command Block must have been set up and the Drive and Motor
        selected.
#78AE   Used to increament Cylinder, Sector, Head to the next Abs.Sector.
        (Including STEP operation)
#78DF   SEEK to track 6, Recalibrate, SEEK Track 'C-reg'
#7921   SEND COMMAND BLOCK !!! (IX + 0AH) is the start, B = # of bytes.
                First it waits until (#7FF4 bit 4) = 0 (Busy flag)
                Then it sends the ComBlk
#7955   Waits until (7FF4 bit 4) = 0
        Calls the SENSE INTERRUPT routine.
        Repeats this until bit 5 of StatusByte0 is set. (Seek End)
        Returns NC if okay, else Cy set if error was rapported.
        (Used by SEEK and RECALIBRATE commands)
#796B   Send "SENSE INTERRUPT STATUS" command block
        Calls the "GET STATUS BLOCK" and return.
#797B   "GET STATUS BLOCK" to (IX+13h) ... as long as there are bytes.
#7993   A delay which much probably be runned under 3.5MHz !
#799C   Sends 2->(7FF3) ?
        Sends 3->(7FF3)
        Sends 2->(7FF3)
#79AB   No hardware access but it looks at 2.nd byte in the Status Block
        If bit 2 is set then A=8:RET    'Record not found'
        If bit 5 is set then A=4:RET    'Data (CRC) error'
        else A=0Ch: RET                 'Other error'
        (Translation into BIOS error codes)
#79BB   READ SECTOR.
        Data is read to where HL points.

        Send ComBlk (7921)
        Read 512 bytes
        CALL #799C
        CALL #797B
#79FC



THESE ADDRESSES ARE IN THE A1GT DISKROM !!! Perhaps they are different in the 
A1ST rom ?

Please only use them to see how to send commands, transfer data, receive 
status block etc.


Here is an example on how to read a sector. When calling this routine the 
head 
must have been placed over the correct cylinder, the motor must be on and the 
drive selected.

RdSec:  LD IX,ComBlk
        LD HL,SectorBuffer      ;Where to put data
        CALL SendCom
        LD DE,#7FF4
        LD B,0
RdSec1: LD A,(DE)               ;Reads the first 256 bytes.
        ADD A,A
        JR NC,RdSec1            ;Jump if StatusReg bit7 was 0.
        ADD A,A
        JP P,RdErr              ;End if StatusReg bit5 was 0.
        LD A,(#7FF5)
        LD (HL),A
        INC HL
        DJNZ RdSec1
RdSec2: LD A,(DE)               ;Reads the next 256 bytes
        ADD A,A
        JR NC,RdSec2            ;Jump if StatusReg bit7 was 0.
        ADD A,A
        JP P,RdErr              ;End if StatusReg bit5 was 0.
        LD A,(#7FF5)
        LD (HL),A
        INC HL
        DJNZ RdSec1
RdSec3: LD A,2
        LD (#7FF3),A
        INC A
        LD (#7FF3),A
        NOP
        DEC A
        LD (#7FF3),A
        CALL GetStaBlk  ;Read StatusBlock
        RET
RdErr:  ;Do a delay. (3.579545 MHz version ! Rewrite it for R800 if needed)
        LD BC,#07A8
RdErr2: DEC BC
        LD A,B
        OR C
        JR NZ,RdErr2
        JR RdSec3

ComBlk: DB #46  ;READ SECTOR
        DB #00  ;Head 0, Drive 0
        DB #00  ;Cylinder.      (Track #)
        DB #00  ;Head number.   (H)
        DB #01  ;Record number. (Sector number)
        DB #02  ;Sector Size.   (2 = 512 bytes)
        DB #09  ;End Of Track.  (Last sector on track)
        DB #20  ;GPL.           (Gap3 length, minimum)
        DB #FF  ;DTL <> 0


I will probably put a GEN file together with this text on the disk. I have 
made a simple Basic program which displays 'CHRN' from disks.

There is 1 thing that I really miss in the FDC. That is the ability to see 
the 
INDEX HOLE, this is important when I want to get the correct and complete 
CHRN 
list for a track. In the currect program I just have to read 18 'CHRN's and 
then the user must pay attention to the list himself.

HG.

l