Open Source, DIY 512KB RAM Expansion

Started by revaldinho, 00:10, 25 April 18

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revaldinho

Quote from: aerobaticant on Yesterday at 11:25Hi @revaldinho, and everyone. I have succesfully created a DIY version of the universal RAM expansion board on prototype PAD board! I changed the JTAG header to be a single in-line pin strip as this it what I have used on other projects using Xilinx devices.

I used an XC9536-15PC44 as I have a few lying around. Looking at the code, and using a 55ns SRAM, I couldn't see a reason why this shouldn't work, unless I've overlooked something important.


Looks great!

You must be a bit of a masochist to build on perf-board, because the project PCBs are easily sourced from many places and also can be had directly from Seeed. Still, it's a nice job. The point to point wiring looks very neat.

Your XC9536-15PC44 should be fine. All the speed grades for the XC9500s should work with all my projects. Even the slowest 15ns ones are way faster than the original LS TTL would have been. 

Quote from: aerobaticant on Yesterday at 11:25Any suggestions of some good (6128?) games to try? ;)

I think the Batman Forever demo is the first thing to try - assuming that you have the 'right' CRTC  ;D

aerobaticant

I agree - there was a bit of masochism, but there's motive in my madness.

I am considering creating an updated version with a schematic (already drawn in KiCad ;) ) and using a newer CPLD.
The Atmel/Microchip ATF15xx family looks to be about the only option currently in production.
I'd also consider moving to an SMD version of the SRAM IC.

Any thoughts?

revaldinho

Yes, the ATF15xx seems like the only 5V compatible part available now, so it's a good choice. I have thought of porting some projects to it but haven't got round to it. The tool chain for Verilog looks a bit more convoluted than the Xilinx one.

As to whether to SMD or not, I just preferred to stick to through hole components to make my projects easy for anyone to build.  My more recent projects are mainly using just 74 series parts to avoid the need for any programming equipment altogether as well as being easy to solder. And they are very retro! The 512Kx8 is the largest SRAM available in through-hole though, so if wanting to do the 1MB or a larger card then I can see it makes some sense to move to SMD for that, where you can get the larger capacities in a single chip. 

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