can the video address point to cartridge port?

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Zamuel_a
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can the video address point to cartridge port?

Postby Zamuel_a » Fri Jan 24, 2014 2:47 pm

I wonder if it's possible to set the video address to point to the cartridge port to see an image that is saved on a cartridge? I think I tested it a few years ago but didn't get anything so maybe the video address can't be set to "anything", just a specific address area.
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Re: can the video address point to cartridge port?

Postby alanh » Fri Jan 24, 2014 6:41 pm

I'm pretty sure it's limited to the addressable memory of the MMU. So no, it won't work.
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Re: can the video address point to cartridge port?

Postby AtariZoll » Fri Jan 24, 2014 8:12 pm

Video is tied to ST RAM, so it's address space can be only in that area (8 to 4MB) .
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Re: can the video address point to cartridge port?

Postby bullis1 » Sat Jan 25, 2014 4:37 pm

Yes, it's an unfortunate limitation of the cartridge interface. Otherwise some interesting NeoGeo-style stuff would have been possible.
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Re: can the video address point to cartridge port?

Postby AtariZoll » Sun Jan 26, 2014 5:30 pm

It is not cart port limitation, but ST's general video concept limitation - as video is generated using RAM, MMU, Shifter and even Glue.
And I don't see why you want to point video base to cartridge port. Instead it just copy cartridge content to RAM and than can easily show image :D
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.

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Re: can the video address point to cartridge port?

Postby Guest » Mon Jan 27, 2014 1:49 am

you can buffer the video and use the blitter to fill the buffer

and via a driver like ide via cart

so you can port over 'frames' so if its a picture you want via the cart port it can be done
but streaming video
i think can be done if you use pperas ide cart and instead of files to a hdd
its frames to a frame store

perhaps as cdrom is 25fps easy i think
yes there is a way to steam to the cart
video

best guy to ask is ppera

putting video into the cart port is done
i had a unit i sent to DAL does this via the cart port

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Re: can the video address point to cartridge port?

Postby Zamuel_a » Mon Jan 27, 2014 7:31 am

I have used the blitter to copy data from the cartridge port so it has not the same limitations as the video shifter. Tobad it can't be done directly. You could stream video from the cartridge port without copy it to RAM first if it had worked.
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Re: can the video address point to cartridge port?

Postby AtariZoll » Mon Jan 27, 2014 8:23 am

Zamuel_a wrote:I have used the blitter to copy data from the cartridge port so it has not the same limitations as the video shifter. Tobad it can't be done directly. You could stream video from the cartridge port without copy it to RAM first if it had worked.


I solved 25 fps video playback, with DMA audio on STE years ago. What you need is hard disk transfer rate of about 1MB/sec, and it is possible with IDE interfaces or UltraSatan, or any newer SCSI drive on Mega STE, or with some ICD adapter. It is with 16 colors per frame.

More interesting is hi-color video playback, so with more than 16 colors, using on-fly palette change ( Spectrum 512 , Photochrome, STeHighcolor).
I solved very big data transfer rates to RAM using little trick - with what you write data from cart. port directly to RAM, without intermediate writing to CPU - what is usual way ( move (a0)+,(a1)+ ). And even better, writes to shifter are done in same way. Possible data rate is over 3.5 MB/sec, so can do even 50 fps with Hi-color ! http://atari.8bitchip.info/movpst.php
There is link to page with technical details.
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.

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Re: can the video address point to cartridge port?

Postby Zamuel_a » Mon Jan 27, 2014 9:32 am

http://atari.8bitchip.info/movpst.php


This is very impressive! :)

I solved very big data transfer rates to RAM using little trick - with what you write data from cart. port directly to RAM, without intermediate writing to CPU - what is usual way ( move (a0)+,(a1)+ )


I think I read about this once on atariage. That you invert the R/W signal between the CPU and MMU to be able to read faster? A move (a0),d0 would infact be a move d0,(a0), but d0 = the data on the cartridge port. Isn't there a risk that the databuss in the Atari and the data you send out from the cartridge port collide and get short circuit so you might damage something?
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Re: can the video address point to cartridge port?

Postby AtariZoll » Mon Jan 27, 2014 12:53 pm

In theory there may be that cart. port, better said CF card will be activated to read, so will drive data bus, and together with that RAM too - but it would be only for few nanoSeconds. Used chips have protections for shorter collisions. In reality, I think that it happens not at all because delays, and that circuits react not on very short pulses. So, if RAM takes read instead write signal for lets say 10-20 nanoSeconds because delay in inverting logic it will not start driving bus.
In any case, I had no any problems on my STE and Mega STE .
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.

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Re: can the video address point to cartridge port?

Postby Zamuel_a » Mon Jan 27, 2014 1:16 pm

I guess it would also be very easy to take the R/W signal out from the CPU so that the cartridge port get's a "normal" R/W function. Unless there is something in the address decoding that prevents writing to the cartridge port at all? So that the ROM3, 4 signals (and maybe the address and data bus to) isn't affected so it's no use.
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Re: can the video address point to cartridge port?

Postby AtariZoll » Mon Jan 27, 2014 3:26 pm

I think that Glue will generate bus error if try to write in cartridge address space. Easy to check ..
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.

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Re: can the video address point to cartridge port?

Postby Guest » Mon Jan 27, 2014 10:42 pm

AtariZoll wrote:I think that Glue will generate bus error if try to write in cartridge address space. Easy to check ..

it will because you need dtack and the cart port does not have dtack pins
but its one wire
just add a gal to the cart to intercept data to the cart via a flash eeprom to store it
again some sort of solder in port is needed
to add such interfaces past the cart port
but to reuse it also
for double bus work perhaps via another dma ic and driver for it or tos mod
perhaps use emu for it
perhaps the cubase dongle guys can use the method more easily for a fix
remember all ram like roms and cart and video and hdd etc is physical addressed space
so its a case of blitting blocks over
much like pperas cleaver cart ide but used with constraints to the rom 3 4 areas

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Re: can the video address point to cartridge port?

Postby AtariZoll » Tue Jan 28, 2014 8:35 am

Possible that adding DTACK logic will make cart port writeable. But it means adding new lines to it. And when it is necessary, I think that better is to do complete new access logic and bypass slow Glue signals (especially in ST) . May use cart port self, as it holds lot of lines: d0-d15 and many address lines, but for additional signals should use some additional connector. 10-16 pins should be enough. Then can use some other address space, which can be much bigger than 128KB.
Famous Schrodinger's cat hypothetical experiment says that cat is dead or alive until we open box and see condition of poor animal, which deserved better logic. Cat is always in some certain state - regardless from is observer able or not to see what the state is.

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Re: can the video address point to cartridge port?

Postby Zamuel_a » Wed Jan 29, 2014 1:56 pm

Yes the Atari had needed a real expansion port. Not to hard to add if there is easy way to hook up to the bus. Are there some ICs that are ALWAYS in sockets on all ST / STE version? Then it would be easy to plug into the sockets to get the signals.
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Re: can the video address point to cartridge port?

Postby Dio » Wed Jan 29, 2014 2:29 pm

In Atari ST Internals they note that they brought DTACK to the outside and found that Glue generated a bus error anyway. I haven't checked this with the timing tester to see if it occurs earlier than the watchdog timer bus errors (the ones that occur in unmapped memory).

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Re: can the video address point to cartridge port?

Postby calimero » Fri Jan 31, 2014 5:29 pm

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