Electron MMFS/2 E00 Cartridge
For some time now I've been using my 16K x 2 ROM/RAM cartridge for the MMFS ROM, ZEMMFS, with a 16K RAM bank to keep PAGE at &E00. About a year and half ago I revisited the design and slightly reduced it's size and changed the PCB colour to match the Electron Ultra.
Now I want to go a step further and reduce its size down to match my 32K ROM cartridges which are just 1.3" tall. To do this I am using surface mount parts for the glue logic and RAM. For the ROM I've selected a socket version of the AT28C256, a PLCC32 EEPROM part, this will keep it as small as possible.
Cartridge comparison..the large one is for MMFS.
This is how the new board turned out, a good fit on the small PCB size..
and this is them is real life..
I soldered up the surface mount part of the cartridge ready to test.
and the RAM can be seen here in ROM position 6, the R attribute is showing that it is being recognised as RAM. A good start.
I then attached the socket for the EEPROM and programmed ZEMMFS v1.60 into the upper part of the ROM. I had tied A14 of the ROM high so the upper part is the correct place to put the image.
With that in place I tested the whole cartridge. It can be seen that the MMFS ROM is in position 7 and it has relocated or claimed its workspace in the RAM in position 6.
Now all my cartridges sit low in the Electron Ultra.
For comparison, the old and new cartridges.
The programming of the AT28C256 was done with the TL866II programmer, a carrier board is required to do this.
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