Page 8 of 8
Re: Oh no! Not another ULA.
Posted: Thu Oct 05, 2023 9:53 pm
by Andy Rea
1024MAK wrote: ↑Wed Oct 04, 2023 10:16 pm
You mean either side of R28…
One side is connected to the ULA.
The other side is connected to the edge-connector and (on a standard machine) to the ROM.
But I presume on a modified machine, the output of the OR gate will drive the ROM instead.
Because the OR gate has one input directly connected to the ‘ULA’, the thinking is that it will switch fast enough?
Why do you think you need a pull-down resistor? A high value would not make much difference as if I understand you correctly, it’s still getting a signal via R28 (680Ω), admittedly very slightly delayed due to stray capacitance. But a low value would draw rather a lot of current.
Mark
no R28 removed from circuit. so ula romcs is only going to ore gate, and romcs from edge is only going to other input and cs at internal rom is directly from or gate output and not connected to any other part of circuit.
what if machine is used without anything connected to edge connector what value will input to or gate see ? i don't want to disable internal rom when nothing connected to edge connector.
and yes to improve the signal integrity and gain a some nano seconds.
Re: Oh no! Not another ULA.
Posted: Thu Oct 05, 2023 9:54 pm
by Andy Rea
Paul wrote: ↑Thu Oct 05, 2023 6:16 am
My guess is he wants to short R28
Remove completly.
Re: Oh no! Not another ULA.
Posted: Fri Oct 06, 2023 12:16 am
by 1024MAK
If R28 is removed, yes, you will need a pull-down resistor. I presume you will not be using 74xxx, 74LSxxx or 74ALSxxx logic, but more modern fast logic.
Mark
Re: Oh no! Not another ULA.
Posted: Fri Oct 06, 2023 8:30 am
by Paul
Maybe inside the CPLD?
Re: Oh no! Not another ULA.
Posted: Tue Oct 10, 2023 9:47 pm
by Andy Rea
Paul wrote: ↑Fri Oct 06, 2023 8:30 am
Maybe inside the CPLD?
yes this probably, heck if your already soldering half a dozen extra wires for additional features, changing your rom to a faster one, and possibly your ram ( whoever is still using internal 1 or 2K ) then heck a few more wires ain't gonna hurt.
Andy
Re: Oh no! Not another ULA.
Posted: Wed Oct 11, 2023 9:47 am
by Paul
Re: Oh no! Not another ULA.
Posted: Thu Jan 25, 2024 8:47 pm
by Andy Rea
Quick update for what it's worth...
Crap happens... My personal circumstance has changed somewhat.
Project on hold until further notice.
Regards Andy
Re: Oh no! Not another ULA.
Posted: Thu Jan 25, 2024 8:52 pm
by Moggy
Understood Andy, Take care buddy and keep in touch.
Re: Oh no! Not another ULA.
Posted: Thu Jan 25, 2024 9:00 pm
by Paul
Thanks for the update. Charlie already told me some weeks ago.
Please keep in touch.
And good luck for your personal circumstances.
Cheers
Paul
Re: Oh no! Not another ULA.
Posted: Thu Jan 25, 2024 9:29 pm
by 1024MAK
Moggy wrote: ↑Thu Jan 25, 2024 8:52 pm
Understood Andy, Take care buddy and keep in touch.
What he said. Look after yourself and your family.
Mark
