> -----Original Message-----
> From: Maarten ter Huurne [SMTP:[EMAIL PROTECTED]]
> Sent: Saturday, March 06, 1999 2:04 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Diskrom modifications
>
> At 04:16 PM 03/05/99 +0100, you wrote:
>
> >I want to make a 'driver' for emulating disk-images from a PC to a MSX.
> The
> >idea is to connect a MSX to a PC and then emulate a disk from data that
> is
> >stored on the PC.
>
> I made a diskROM like that which reads DSK images from PC to MSX through
> the JoyNet cable. At the moment, it is read-only and works under DOS1
> (MSX-DOS and BASIC).
>
> I can send you the code if you like.
Please do! I can use any help on this subject.
> The main problem with the code is that my protocol cannot recover from
> errors. The protocol
> is constructed in such a way that errors are rare, but they do occur
> sometimes (about once in 50 megs).
>
> The PC side is a simple "sector server" written in Delphi. You can select
> a
> DSK image and a volume inside that image (for multi-disk images). It also
> reports a disk change signal, which makes caching at the MSX side
> possible.
>
This is great! I downloaded the diskrom disassembly from Alwin
Henseler, this will also help me.
> >Now, I want to know if I can get away with just writing
> >new routines for PHYDIO etc. (i.e. changing the JP's in the diskrom at
> >4010h, 4013h etc. to my routines which do the communication with the PC).
> I
> >only want to change the physical I/O part, everything else should then
> still
> >work.
>
> You only have to implement the I/O routines located at #4010 and higher
> (get DPB, read sector, disk change, format etc). You don't even need the
> other routines, because they are already located in the main diskROM.
>
But if you do this, I guess it is not possible anymore to use the
normal diskdrive, or...
> Then you need some way to connect your routines to a drive letter. What I
> do at the moment is to modify the table located at #FB21, using a CALL
> statement in BASIC. What would be better is to have the extra drive added
> at boot time. Can someone explain how to do this?
I don't yet know, but I'm working on this.
> >I want to integrate this diskrom in a cartridge that holds the interface.
>
> I am very interested if you can make a high-speed parallel connection.
> JoyNet, which is a simple serial connection, is slow for DSK emulation (a
> bit slower than a real drive).
Well, I don't think it can be that hard. Especially if you use
components in the interface that can do the error-handling (that's why I was
thinking about ARCnet). But I don't have anything concrete yet, just
investigating the possibilities. I was also thinking of a way to use the
joystick-interface, but then use 4-bit parallel or 8-bit parallel in one
direction and 1 or 2 bit in the other direction (because I guess reading
will occur more often than writing).
Greetings,
Patrick
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