VS23S010 - 1Mbit SPI/8-bit Parallel Bus SRAM

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uze6666
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Re: VS23S010 - 1Mbit SPI/8-bit Parallel Bus SRAM

Post by uze6666 » Thu Mar 10, 2016 6:19 am

Uze, with that type of chip.... we can forget the AD725? also as far as we can add a NTSC XTAL at the normal frequencie (it seem that the chip can multiply by 8 the orgininal NTSC frequencie) would it be difficult to add support for the atmega1284? I think overclocking the Atmega644 will not be necessary? or i am wrong?
Well, not really. Sure the 28Mhz clock was used to clock the ad725 (requires 14.3Mhz) but the added clock rates also means more cycles for processing and speeding up the "pixel clock". Unfortunately the Atmega1284 can't be overclocked, it's very unstable at these frequencies.
more memory, a video buffer, what will be the inconvenient of putting this chip with an atmega1284? I don't know exactly what effort have to be done to upgrade the actual Uzebox to be honest..
It totally doable to use a 1284 clocked at 20Mhz with the VS23S010. But it would be a very different things than the Uzebox. At first thought, the kernel can't be universally retrofitted since it can do on the fly some thing the VS23S010 can't (palettes for instance). But I could be wrong. Perhaps it could be possible to stream the pixels from portC straight to the spi ram. Needs some thinking.

Lee's idea with the ESP8266 is excellent! You could then indeed drive all those inexpensive LCD car monitors and make all kinds of inexpensive IoT devices like Panu's idea. :mrgreen:

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Re: VS23S010 - 1Mbit SPI/8-bit Parallel Bus SRAM

Post by panu » Thu Mar 10, 2016 9:30 am

Perhaps it could be possible to stream the pixels from portC straight to the spi ram. Needs some thinking.
Quad SPI or parallel 8bit bus is fast enough to stream the whole display memory in real time.. I remember calculating that 180 fps would be possible.

That means that you could use the VS23S as a simple TV DAC. I'm not sure how I feel about it.. It would leave a lof of VS23S features like the hw blitter unused; with the blitter you can do things like full screen scrolling and tile graphics even with a slow microcontroller like the one in Arduino. But with a fast CPU (100MHz+++) which is fast enough so that likes to draw the whole framebuffer in software; that kind of CPU might use the VS23S as a simple TV DAC.

Could the Uzebox use it as such? Use port C for pixel upload? You'd have to generate the write clock for the data; is it doable? (Write PORTC & WR high; then write WR low). That might be a forward path from the existing Uzebox architecture.
But it would be a very different things than the Uzebox.
That's true. The Uzebox is very hands on drawing the frame, and the challenge is to do some nifty things with pixels in microsecond or nanosecond scale. That's an engaging challenge in its own right, and very satisfying for the right type of person. And for the existing Uzebox you've done some amazing things such as the emulator. With the VS23S010 it would be different. A step higher in the abstraction level. You'd have a full frame buffer RAM and the VS23S handles all timing and control of drawing the TV picture. The microcontroller's task is to manipulate the display memory by writing to the memory, commanding the blitter and perhpas manipulating screen modes and line pointers. Draw pictures instead of lines. You're operating in millisecond scale instead of microsecond scale. New things are possible and it's a different challenge. Different, but equally fun, I would hope.

It's totally doable to use a 1284 clocked at 20Mhz with the VS23S010.
That's right, with the VS23S you don't have to run the CPU at NTSC/PAL frequencies, except perhaps to save the cost of a crystal, perhaps.


-Panu

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Re: VS23S010 - 1Mbit SPI/8-bit Parallel Bus SRAM

Post by TonyD » Tue Dec 13, 2016 1:46 pm

sorry for revisiting an old thread..

Did anyone try out or experiment with the VS23S010 chip?

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Re: VS23S010 - 1Mbit SPI/8-bit Parallel Bus SRAM

Post by uze6666 » Mon Dec 26, 2016 1:26 am

It's a shame, but for me, no. Panu was kind enough to send be a couple samples, so if someone is up to test it, i can send him one or two.

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