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PostPosted: Wed Aug 08, 2018 4:02 pm 
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I thought this was odd, and potentially useful, but as it's 3V only it's just a little off-topic.

It's an SRAM chip, with either an 8-bit parallel or an SPI interface, with an on-board video output circuit controlled by SPI and with access to the RAM. You can daisy chain up to four chips. The 8-bit parallel access seems to be byte-sequential in some way - there's no conventional address port.

Oh, and it's got some I/O too. So if you have an SPI capability, or if you're happy to bit-bang it, you can get storage, video, and/or some GPIO, all in one chip.

Image

It appears that they started with a RAM chip, and someone (Panu-Kristian Poiksalo) had the bright idea of adding video capability as it's just a few gates:

Quote:
And at a meeting, our CEO asked if we had any other ideas for the product. And so I said that if we just add a couple of counters inside, we could make a pattern generator that could be useful for "various purposes". He said that should be ok, if indeed it was "just a couple of counters" and didn’t make the chip a testing nightmare.
…​
I actually came to the lab during the weekend and wrote the configuration for a minimalistic NTSC modulator on that tiny CPLD. When our CEO saw it, he asked if we could fit it inside our IC. And I said, sure, its something like 10 to 20 flip-flops. But with a little more, we could make it much better. He asked how much better, and I said full color (my demo had 14 colors - sync level, burst level and 14 indexed colors formed with VHDL combinatorial logic statements). Of course we would need to put a DAC inside, but no problem, our company is expert with DACs.

- from History of the BASIC Engine, being a single-board retro-ish hobby computer.

Edit: found the guide for the chip - it has a DMA engine too, aka blitter.


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PostPosted: Wed Aug 08, 2018 10:14 pm 
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Nice find.... interesting chip indeed. Did a quick search and found a Hackaday project based on it:

https://hackaday.io/project/21097-ntscp ... lay-shield

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PostPosted: Thu Aug 09, 2018 12:30 am 
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I thought this was odd, and potentially useful, but as it's 3V only it's just a little off-topic.
I would say it's on-topic if you have a 6502 that can run at 3V :)

Another neat chip I have used with microcontrollers is 23LC1024. It is 128k of SPI SRAM and available in DIP8. The guy who worked on the Flea projects was using them to generate video somehow. You can put the chip in a burst mode where four of its lines are outputs and it outputs the next half byte every time it gets a clock pulse.


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PostPosted: Thu Aug 09, 2018 6:16 am 
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I like that! Video by ultra-simple DMA.


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PostPosted: Thu Aug 09, 2018 10:47 am 
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Not only video, apparently - it can also be used as an audio buffer or one channel of a wavetable synth. And not only *composite* video; put three of them together and you can have an analogue VGA/RGB output, though I haven't yet worked out how best to produce the separate sync signals.


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PostPosted: Thu Aug 09, 2018 12:39 pm 
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Chromatix wrote:
Not only video, apparently - it can also be used as an audio buffer or one channel of a wavetable synth. And not only *composite* video; put three of them together and you can have an analogue VGA/RGB output, though I haven't yet worked out how best to produce the separate sync signals.


They have another chip for that: http://www.vlsi.fi/en/products/vs23s040.html

It has a four channel output that can do RGB...


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PostPosted: Thu Aug 09, 2018 1:27 pm 
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Jeff_Birt wrote:
They have another chip for that: http://www.vlsi.fi/en/products/vs23s040.html

It has a four channel output that can do RGB...


BGA it seems...my old eyes and hands couldn't handle that. lol.

However, I have to admit my new glasses are doing a pretty good job at seeing things! I was soldering the other day without my giant magnifying glass!

Back OT...I still think the Propeller is a good option too. And it can run in parallel or serial. Now, it's a little more expensive. $8 + $2/EEPROM + $1 oscillator but that's not the end of the world for hobby projects.

My only complaint about the Propeller is that interfacing much more than 1 MHz in parallel may not be possible.

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PostPosted: Sat Aug 11, 2018 11:47 am 
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Unfortunately the 8-bit bus doesn't look like it could be used with a 65xx bus without significant fiddling.

The reason it has not address pins is because it essentially just maps the SPI commands on to the 8-bit bus - you write in a command, three address bytes, and then reads or writes from that address sequentially. A bit irritating perhaps, but not a deal breaker, until you consider that all of this has to occur with XCSPAR (the chips equivalent of a CE) has to be low the ENTIRE time, which doesn't work with normal 6502 address decoding because of the intervening opcode fetches would deassert CE.

I think the easiest way to talk to it over 8-bit mode would be to use a GPIO to control XCSPAR and then qualify this chip's RE/WE with what would have been this chip's CE signal.

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PostPosted: Sat Aug 11, 2018 11:49 am 
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Ah, that's not so handy. Although, presumably there's some kind of clock or strobe which latches the bus as valid? Could the bus happily wiggle in between times?


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PostPosted: Sat Aug 11, 2018 7:57 pm 
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I'm not 100% sure what you mean, but I don't think so. The datasheet section on the 8-bit comms mode only shows WE, RE and XCSPAR in the relevant timing diagrams. It also refers to WE and RE as the Write Clock and Read Clock, respectively, which is a bit odd.

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PostPosted: Sat Aug 11, 2018 8:00 pm 
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Ah, so perhaps WE and RE are 8080-style, acting as strobes to capture the value. I should perhaps read the datasheet instead of blathering...


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PostPosted: Sun Aug 12, 2018 12:47 am 
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Why not drive it with a VIA?


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PostPosted: Sun Aug 12, 2018 3:47 am 
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To my mind, most of the point of an 8-bit interface(especially on a chip like this) is to be able to put it fairly directly on a processor's bus.
It looks fairly hard to do that as it is. You'd have to have some kind of extra hardware to fake the commands onto the bus, and probably wait-states, too.


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PostPosted: Sun Aug 12, 2018 9:48 am 
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They might have had something different in mind, like driving the SRAM from programmable logic.


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