RetroFocus2015
New Member
Hi,
1. Oh i didnt realize that you were not using the entire 64k address space. With 32k ram and only 2k rom, you have some of that address space available, unless of course you intend to increase the size of the rom, and then you should use i/o anyway. But if you can limit the rom to say 16k, then that gives you one address line that wont be used for addressing anything when the ram isnt selected with A15, so you can use that AND'ed with A15 to access 16k of something else, like your sound chip or similar...
2. An edge connector...
You mean a PC board edge connector? To plug into what, the PC computer or your own mainframe card cage?
1. As I can best describe it, the design is constantly changing in my mind, using parts I now have available. At the moment I have a AT28C256 32K EEPROM on the schematic. With import costs and - I suppose - rarity of older parts it seems a lot easier to obtain the newer parts with the bigger amounts of RAM and ROM on less chips. I think I'll use the 32k EEPROM and cram as much useful stuff on there as possible, like ASCII characters etc.
2. Something like this **broken link removed** You could plug just about anything into these expansion ports like joysticks, RAM upgrades, printers, light pens etc using an interface like this one on a TRS-80 https://www.nightfallcrew.com/09/07...s-80-modello-mc-10-con-espansione-ram-di-16k/