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PicoRAM Ultimate GitHub Repo released

LambdaMikel

LambdaMikel

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Jan 25, 2020
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hackaday.io

PicoRAM Ultimate

PicoRAM Ultimate is the ultimate storage solution for single board computers (SBCs) / CPU trainers from the 70s and 80s. It emulates: - up to 4 2112 SRAM chips: it replaces the 512 bytes of stock SRAM in the Heathkit ET-3400; alternatively, - a 2 KB memory expansion for the Heathkit ET-3400...
hackaday.io hackaday.io

github.com

GitHub - lambdamikel/picoram-ultimate: An SRAM Emulator and SD Card Interface for Vintage Single Board Computers

An SRAM Emulator and SD Card Interface for Vintage Single Board Computers - lambdamikel/picoram-ultimate
github.com github.com
 
PicoRAM Galore:


... and LabVolt RAM test - Firmware Version 1.2 passes this test now:

 
I have a bug in the ET-3400 IO exp. header in the current PCB version - please see the updates on the Github!
When I installed the IO header in my ET-3400, I selected the wrong NC PIN for the RE signal (counted "6 from the top right" instead of "6 from the top left"...), hence, resulting in a PCB error.

Fortunately, there is an easy fix: pull JP9 completely, and in addition, if you are using the IO header connection, route a DuPont cable from the left pin of JP9 to the RE socket:
ultimate-heathkit1.JPG

picoram-re-bug-1.jpg
 
Revision 2 is in production, which fixes the RE flaw (wrong RE pin position on the expansion header); it also routes more address lines into the GAL decoder and supports 4 KB now:
Screenshot (106).png
 
Last edited:
ROM emulation in PicoRAM is running stable now - I disabled the Write Enable (/WE) signal for this. I will change the firmware (-> Version 1.8) such that ".ROM" files will get this auto "memory protection" enabled, and ".RAM" files obviously won't:

 
Board Rev. 2.0 released - this bumps up the ET-3400(A) emulation to 4 KBs, for either RAM or ROM. Address decoder is more flexible. Firmware version 2.0 as well. And, I have fixed my ET-3400 extension header - RE position is correct now, no more bodge wires into the RE terminal block required.


github.com

GitHub - lambdamikel/picoram-ultimate: An SRAM Emulator and SD Card Interface for Vintage Single Board Computers

An SRAM Emulator and SD Card Interface for Vintage Single Board Computers - lambdamikel/picoram-ultimate
github.com github.com
picoram-rev2.jpgpicoram-rev2-ram.jpgpicoram-rev2-rom.jpg
 
In the meantime, I experimented with adding some IO-extensions to PicoRAM. Here is a first "Hello World" for the Heathkit:


Eventually, this should at least offer some of the text- and graphics capabilities for the ET-3400(A) that I already had 3 years ago with PicoRAM 2090 for the Microtronic:

 
... and here we have a proper scrolling text display for Towers of Hanoi:


You can probably guess what's coming next? ;)
 
Alright, I am done for now - last email for now on this.

Taking a bit of a break now: mission accomplished, thanks to CoPilot who wrote 80% of the code!

 
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