4040 dual floppy

History and Preservation Issues

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Kakemoms
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Re: 4040 dual floppy

Postby Kakemoms » Tue Sep 13, 2016 1:52 am

srowe wrote:
Kakemoms wrote:There are a few bytes in the Kernal that are free or unused, but is it enought...


By my counting there are 118 bytes of unused space (non contiguous). I don't think that would be enough.


Hmm.. no, thats not enough, even compressed.. How did they push JiffyDOS into that ROM. :shock:

eslapion
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Re: 4040 dual floppy

Postby eslapion » Mon Sep 19, 2016 4:48 am

Kakemoms wrote:
srowe wrote:
Kakemoms wrote:There are a few bytes in the Kernal that are free or unused, but is it enought...


By my counting there are 118 bytes of unused space (non contiguous). I don't think that would be enough.


Hmm.. no, thats not enough, even compressed.. How did they push JiffyDOS into that ROM. :shock:

The tape routines are removed from JiffyDOS.

Perhaps you don't need the datasette routines if you implement IEEE-488 for userport in Kernal.

If one combines the serial port with the User port you will get 14 port lines. The serial port can be routed with a buffer to free it for other devices when the IEEE isn't needed.

Then take out the IEC routines too. There's your space.
No one can do everything. Everyone can do something.

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Kakemoms
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Re: 4040 dual floppy

Postby Kakemoms » Sat Sep 24, 2016 11:03 am

Kakemoms wrote:
srowe wrote:
Kakemoms wrote:There are a few bytes in the Kernal that are free or unused, but is it enought...


By my counting there are 118 bytes of unused space (non contiguous). I don't think that would be enough.


Hmm.. no, thats not enough, even compressed.. How did they push JiffyDOS into that ROM. :shock:


Well, I finally got my order of 12x2pin userport edge connectors from Taiwan. I though I had ordered 6, but it was 60 pcs in the package... lol.

So I really have to do this now. No need to have 60 connectors laying around. I have looked at the disassembly which is interesting. The schematics Eslapion pointed to also shows that one can do this with 16 I/O lines. The userport has 8+5 general I/O lines from one VIA plus another one that goes through a NOT gate to ATN (so it becomes output only). That can be used to switch the multiplexer. The user port also has two shift register I/O outputs, so a total of 16 lines.

I can draft a schematic once I have read through the disassembly and see if it works. I am missing the 75160/75161, but I can replace them with some 74LS245 on my breadboard to see if I can get it working.. Well, there goes October. :lol:

Edit: Here is my suggested V_Link replica. Its going to need new software because the V-Link ROM does not make sense with the available signals on the Userport. It also looks like it can be done without using output 9 on the Userport (which is connected to the serial port). Thus, the IEC should work as normal. Joystick port needs to be unused for this to work.
V-LINK-replica.png


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