Products > Vintage Computing

Eurorack modular 8085 computer

<< < (15/15)

MK14:

--- Quote from: ChristofferB on April 10, 2016, 08:24:04 pm ---Diode rom matrix boards are difficult to make on strip/hole/veroboard. The layout is awkward.
Back in the days, there were dedicated cards, with traces lain out for diodes to be fitted easily.

--- End quote ---

Possible way of making a cheap matrix/switch plug board, diode array.

Could you do it, via headers and 2 pin shorting links, to make a super cheap/quick/easy matrix board.

I would imagine the diodes can be done. Maybe you can get SIL/SIP diodes, example shown below:
Possibly soldering them on the other (reverse) side of the board, if you are happy about that.









MK14:
But a microcontroller, such as the 8051 or something, would also be a good solution. Potentially doable in the 1980's, so your retro/vintage qualifications/requirements, are still met!

ChristofferB:
You're right, that would be a completely viable way of doing it! I think I'll go for actual rom booting for now. Last time I tried diode matrix roms I lost all interest half way through:

ChristofferB:
I just noticed a rather large design fault with the system. It has very poor handling capabilities for multiple interrupts. I've added four interrupt lines in my backplane bus, deviating from the standard ECB bus pinout, simply by removing unused pins (like D8-15, I'll never go 16bit in this system), called GPINT0-3 that can either be inputs for the 8085's many interrupt lines (all the RSTx.x's) or a 8259 interrupt controller. With that, I could have only one interrupt line going to the cpu.

Not having multiple interrupts would be a nightmare. Also, one could just have a 8259 per board, but it'd be hard to mask between them - two boards could still interrupt at the same time. Now I can have a master 8259 on the CPU card, branching to 4 out on other cards, giving up to 32 interrupting peripherals.

The other option being having the 8259 on the CPU card, and then have a secondary (ribbon cable with DIP headers?) bus running all the interrupts. It still may be necessary, but it's not very elegant.

 

Navigation

[0] Message Index

[*] Previous page

There was an error while thanking
Thanking...
Go to full version