2-chip external memory mapper 512K

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By RetroTechie

Paragon (1563)

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26-08-2011, 04:23

Hello again! Haven't updated my site in a while since other Real Life (tm) activities ate my free time... Eek! But finally found some time to finish a final round of testing, update docs, make some pix, slap together a webpage & upload it:

http://bitcycle.org/retro/msx/512k_mapper/

A 512 KB external memory mapper built with just 2 IC's... Logic sits inside a small programmable logic IC, and for those who like to tweak things, source code of the logic inside that part comes with it. Very extensively tested. Have fun!

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By Manuel

Ascended (19270)

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26-08-2011, 23:23

Great, thanks for sharing!

By edoz

Prophet (2465)

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05-09-2011, 22:43

It's quite cool indeed..i like the pictures Wink .. for me it looks a little small for my 'soldering' skills Wink

By JINsMac

Expert (77)

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06-09-2011, 07:28

Thank you very much for sharing!

By dhau

Paragon (1570)

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07-09-2011, 00:00

Pretty cool, I'll order those cplds and try it. How did you program them? Some special cable?

By RetroTechie

Paragon (1563)

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10-09-2011, 01:03

It's quite cool indeed..i like the pictures Wink .. for me it looks a little small for my 'soldering' skills Wink
0.8 mm pitch - about the smallest I can solder wires onto (tip: I used wires pulled from 80-wire IDE cable). It takes practice, but it's doable. These parts also come in 44p PLCC, that's easy to solder or put in socket. For comparison: MSX engine IC (S3527 or S1985) have even smaller pitch.

And that's IMO a big problem with these CPLD's: if you want significantly more logic, you get IC's that are (almost?) impossible to hand-solder. Eg XC95144XL is a popular part (I have one here), but 100 pins on 14x14 mm. IC - good luck with that. Crazy Adapter boards are impossible to find or ridiculously expensive.

How did you program them? Some special cable?
Home-built Parallel Cable III (schematic is on Xilinx site), still works with latest ISE 13.2 - see '1st CPLD project' on my site for details. IIRC I soldered some wires + capacitor(s) to be able to power it, and 4 wires for programming. After programming those 4 JTAG pins can stay disconnected. When making the CPLD design, you have much freedom in what signal you put on which pin, and that helps a lot to make the rest of the soldering job easier... Smile

By msxegor

Master (183)

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17-09-2011, 20:29

With current SRAM chips 1 meg memory is possible with just a memory chip and a 64-cell PLD.
Unfortunately, bigger memory chips are all 3.3 volt..

By sd_snatcher

Prophet (3642)

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17-09-2011, 21:05

@msxegor

I was looking for 1MB SRAM chips some time ago. Do you have the part numbers and makers for those?

By msxegor

Master (183)

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17-09-2011, 21:21

Samsung K6X8008 - unfortunately, only in not-DIY-friendly TSOP-44 packages. But still 5V-friendly

By RetroTechie

Paragon (1563)

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18-09-2011, 02:50

Thanks for that type number! A while ago I found some other types:

Cypress CY62158ELL - 1Mx8 bit, 5V, 44-pin SMD package with 0.8mm pitch.
Brilliance Semiconductor BS62LV1600E - 2Mx8 bit, 3~5V, 44-pin SMD package with 0.8mm pitch (going for some 19 Euro's/pop @Farnell).

Hobbyist-unfriendly indeed, but doable & OK for small series of... whatever. Good to have a shortlist of these types because 5V, >512K (and x8 bit) SRAMs are pretty uncommon.

By ericb59

Paragon (1098)

ericb59's picture

26-08-2013, 20:05

Hello there ,

Is it possible to have this translated into Altera Quartus software ?
(well, I have no skill to do it myself !)

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