Multirom cart - UPDATE

Talk about programming CreatiVision (except games programming). Projects of homebrew hardware are also welcome.
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MADrigal
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Re: Multirom cart

Post by MADrigal » Sat Jan 04, 2014 6:26 pm

OK I officially want one of these!

If you are to number them, I sign for number 1 :-)
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carlsson
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Re: Multirom cart

Post by carlsson » Sat Jan 04, 2014 11:54 pm

Cool!! However I wonder how much difficulty it would be to switch in ROM by software, now that we have a bunch of Creativision programmers who with small efforts at least could put together menu software, instead of going through DIP switches. Probably a bit too late now if you already had the boards made, unless you can bypass the DIPs for a software solution.
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Scouter3d
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Re: Multirom cart

Post by Scouter3d » Sun Jan 05, 2014 9:13 am

Hi Carlsson,

A menue driven Multiromcard is a great Idea!

Do you have any idea, how this could be achieved on the Hardware Level? I know there are cartridges out there (Intellivision, Videopac...) that manage to do it, i thought about such a Feature for my own projects, but i have no idea up to now...

Ideas anyone?

Greetings TOM:0)
pikkey
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Re: Multirom cart

Post by pikkey » Sun Jan 05, 2014 9:26 am

carlsson wrote:Cool!! However I wonder how much difficulty it would be to switch in ROM by software, now that we have a bunch of Creativision programmers who with small efforts at least could put together menu software, instead of going through DIP switches. Probably a bit too late now if you already had the boards made, unless you can bypass the DIPs for a software solution.
I had think to this solution too, but..
In the beginning I've found a Creativision without cartridges. After cleaned and checked it, I had the desider to make it work in some way.
Started searching for something on the web, I'd found this site (Madrigal) where there were exactly what I was searching for...but out of stock. :) Moreover, the available games was very few, and I was asking myself: how many Creativision there is around..?
That's because Paolo (my Master :) ) drove me to build this new cartridge, following the concept of the original Multicart.
Since we had to produce a multiple boards (to decrease the cost of production of a single board) and we had no idea about the "hipe" around this , we choose to produce a very little number of them, focusing to the low final cost, and dropping any ambition about sophistication and packaging. Just the essential.

PS: Forgive me about my english :oops:
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carlsson
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Re: Multirom cart

Post by carlsson » Sun Jan 05, 2014 10:31 am

Sorry, I have no insight in how to use hardware to shift cartridge images. Probably some I/O pins like the ones used by e.g. the parallel interface? For that matter, also the VIC-20 Megacart and others use software driven menus. I see one problem in that Creativision games need to be reset in order to play them, so the question would be how to get back to the menu software, perhaps holding down a fire button while pressing the reset button? Still, it would mean some menu software must be in place all the time, automatically returning to last selection if no other buttons are held down.

So for the moment being, perhaps the DIP solution is not so bad after all, and we can try the software menu solution for a future SD solution that also would allow us to store whichever file names we want on the card, to be displayed on screen. See e.g. the AtariMAX and C64 EasyFlash carts for ideas, although both use internal Flash chips rather than SD storage.
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Scouter3d
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Re: Multirom cart

Post by Scouter3d » Sun Jan 05, 2014 6:07 pm

carlsson wrote:Probably some I/O pins like the ones used by e.g. the parallel interface?
Hi Carlsson,

The I/O Address is a good idea, i think about a flipflop (72ls374) to store 8Bits at the adress of the I/O Interface, and connect the Output to the upper addresslines of the "Multi" Eprom to select the different banks... ?????? but i do not know, if the state of the flipflop is defined at powerup...

One could put the menuprogram in bank 0 and poke the selected itemnumber to the I/O address, then the CV will "hang" because of the switching and after a reset, the selected game should start...

to go back to the menue a resetbutton on the cartridge could be added...

No idea, if all the above would work ;0)

TOM:0)
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Mobsie
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Re: Multirom cart

Post by Mobsie » Sun Jan 05, 2014 8:03 pm

On one of my VIC-20 MultiCart are only the Eprom and 3 IC`s.
One SN74LS273 Flip-Flop, one SN74LS08N Positive-and-Gate and one SN74HCT14N Inverter.
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Scouter3d
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Re: Multirom cart

Post by Scouter3d » Mon Jan 06, 2014 7:50 am

Thanks Mobsie,

74LS273 or 74ls374 (both are octal D- edge triggerd Flip-Flops, the 273 has a CLEAR Input to reset the chip and the 374 has an OE instead...) both should work...

Greetings TOM:0)
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Scouter3d
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Re: Multirom cart

Post by Scouter3d » Mon Jan 06, 2014 9:25 am

Hi,

I put together a first schematic idea for the menue driven multicart...

the 74LS139 selects Address F000 (which should be free)
I NOR'ed this with the R/W Signal (to be sure the Databus is ready and to get a positive edge flank for the flip-flop)

Any ideas, comments?

Update V2.0: Schematic updated (Error in address decoding)
Update V3.0: Schematic updated, one chip removed due to use 74LS138 instead of 74LS139

TOM:0)
menue_cart_schematic.jpg
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Last edited by Scouter3d on Mon Jan 06, 2014 11:00 am, edited 2 times in total.
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Scouter3d
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Re: Multirom cart

Post by Scouter3d » Mon Jan 06, 2014 10:25 am

sorry, i think there is an error in my schematic (in the 74LS139 section...)
will post again, whe i figured it out...

TOM:0)
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