Oh no! Not another ULA.

[Lardo Boffin]

Looking awesome.

I have several zeddies in need of a ULA based rescue so happy days!

[Paul]

With those free bits, could you offer faster turbo modes?
This way we could try out up to which speed our Zeddy still works

[Andy Rea]

With those free bits, could you offer faster turbo modes?
This way we could try out up to which speed our Zeddy still works

You Want Quad speed ? in theory should work.. BUT you WILL need a faster CPU and The MOTOROLA type rom (or your own fast replacement) the NEC roms dont even work at double speed !

Bngger!!! the motorola rom is too slow also.

[Paul]

My ROMs are 45ns and my CPU 20MHz

[Andy Rea]

My ROMs are 45ns and my CPU 20MHz

That will be plenty fast

I haven't done any calculations but can tell you that a 250ns eeprom ( at28c64-25pc) works okay

[Paul]

And in case you are not short of macro cells:
I would like to have a WR signal that doesn't come active in the lower 8K address space.
So I could use a 32K Autostore RAM as combined ROM and RAM (RAMCS and ROMCS ORed) in order to have a three chip zeddy
I once tried and it worked but could not be reseted because the bottom 5 bytes are overwritten.
As the ROM content was locked it needed a power cycle to restore the ROM again.

[Andy Rea]

And in case you are not short of macro cells:
I would like to have a WR signal that doesn't come active in the lower 8K address space.
So I could use a 32K Autostore RAM as combined ROM and RAM (RAMCS and ROMCS ORed) in order to have a three chip zeddy
I once tried and it worked but could not be reserved because the bottom 5 bytes are overwritten.
As the ROM content was locked it needed a power cycle to restore the ROM again.

Would altering ROMCS to be only active when ~RD is low also ? have any impact on other things ?

[Paul]

That sounds like another possible solution. Great idea!
This way I just connect normal !WR directly and RAMCS and ROMCS via diodes.

[Andy Rea]

i forgot about fetching character data during the refresh when the screen is been drawn...

[1024MAK]

If we don’t find any better uses for spare bits, if there are spare output pins, maybe use for Blinkenlights

This would normally be under software control, hence the Zeddy could gain a very simple output. If you don’t want a Blinkenlight, it could drive something else via suitable circuitry (transistor) such as a relay.

Mark