Generic driver for the CS/A65 SCSI interface
--------------------------------------------

This is the generic driver for the CS/A SCSI interface, written for
the 6502 CPU.

The hardware is derived from a very old SASI interface described 
in the german elektor magazin.
The schematics can be found in csascsi1.{gif|ps}
A description and parts list are in csascsi1{desc|parts}.txt.

The software runs on the C64 with the C64-CS/A65 bus adaptor
(See http://www.tu-chemnitz.de/~fachat/8bit/c64/csa/index.html)
as well as on a CS/A65 computer.
(See http://www.tu-chemnitz.de/~fachat/8bit/hardware/csa/index.html)

To build the driver you need the xa65 6502 cross assembler.
(See http://www.tu-chemnitz.de/~fachat/8bit/cross/xa/index.html)
It should be easy to patch the source for another assembler.

New with 1.1:
-------------

- the pc partition scanner handles extended partions better 
- a C64 binary is included (as "mainc64"). Simply LOAD and RUN it
  if you have the SCSI-interface at $de00. 
  (It doesn't check if it's there!)

Driver Description
------------------

The driver is divided into several parts:

csascsi1.a65 contains the low-level routines to scan the SCSI bus
	and to read/write sectors for the CS/A65 SCSI card. 
	To use another hardware this module can be replaced.

part.i65 defines a general interface to read and write blocks in a 
	partition. Also the partition table format is defined here.

pcpart.a65 uses the low-level routines to scan the devices for 
	PC-style partition tables. They are registered in the partition 
	table. To use a different type of partition tables 
	(Amiga for example), replace this file.

paccess.a65 implements the pread and pwrite functions to read and
	write blocks in a partition with the use of the partition table.

print*.a65 are some help routines to print debugging output when 
	the routines are used in an OS/A65 1.3  or C64 environment.
	It is not needed without output or has to be replaced for 
	another operating environment.

main.a65 is a simple test program. It also includes the driver for
	assembling with the xa65 crosscompiler and the OS-specific 
	startup code.


Comments
--------

This is the very first version. There are sure some bugs. 
Error handling is miserable. 
The hardware only works as single controller and only as ID 7.
There is no fdisk program - it would be partition-style dependent
and would use the low-level driver.
If in doubt, read the source :-)

Here is the sample output of the main program:

-------------------------------------------------------------------------
>l"maincsa" 400:0B14
>g 400
CS/A65 SCSI driver

Resetting SCSI bus
Device select timeout 00
Device select timeout 01
Device found 02
SEAGATE ST1096N         [Type 00, SCSI Rev. 01]
       [Blocks: 00028091, Byte/Block: 00000200]
Device select timeout 03
Device found 04
IBM     DCAS-34330W     [Type 00, SCSI Rev. 02]
       [Blocks: 008132FF, Byte/Block: 00000200]
Device select timeout 05
Device select timeout 06

Scanning for PC-type partitions

Found Direct Access Device 02
Partition Type 04, Device 02, First 00000020, Len 0000F7E0
Partition Type 05, Device 02 (extended)
Partition Type 06, Device 02, First 0000F820, Len 000187E0

Found Direct Access Device 04
Partition Type 06, Device 04, First 00000020, Len 001DB7E0
Partition Type 05, Device 04 (extended)
Partition Type 83, Device 04, First 001DB820, Len 0000A7E0
Partition Type 05, Device 04 (extended)
Partition Type 83, Device 04, First 001E6020, Len 001F47E0
Partition Type 05, Device 04 (extended)
Partition Type 82, Device 04, First 003DA820, Len 0003C7E0
Partition Type 05, Device 04 (extended)
Partition Type 83, Device 04, First 00417020, Len 003FBFE0

>m e1e e5e
>,0E1E 04 00 02 00 00 02 00 00 20 00 00 00 E0 F7 00 00:........ ...a/..
>,0E2E 06 00 02 00 00 02 00 00 20 F8 00 00 E0 87 01 00:........ 0..a...
>,0E3E 06 00 04 00 00 02 00 00 20 00 00 00 E0 B7 1D 00:........ ...ao..
>,0E4E 00 00 04 00 00 02 00 00 00 70 43 30 08 04 71 00:.........pC0..q.
>
-------------------------------------------------------------------------

As you can see the driver is pretty small (the whole text segment is
about 1k without print + about 180 byte for partition tables etc. 
(Of course it needs buffers to read & store the sectors read from disk)

It can also handle multiple devices as well. The IBM 4G Ultra-Wide SCSI-II
(with Wide-SCSI -> SCSI adapter) is handled as well as the old Seagate
ST1096N SCSI-I at the same time.

The partition table shows three usable partitions, of types 4 
(FAT 16 bit < 32M) and 6 (FAT 16 bit >= 32M) and
on (SCSI-) devices 2 and 4. the 4th to 7th byte are the bytes/block,
then the first block and the length of the partition on the device.
The other partitions found but written to the partition table are
Linux partitions :-)

There will be a binding to the fsibm 12/16 Bit filesystem for OS/A65.

Have fun
Andre Fachat                                           13 June 1998