Andy Rea wrote:I hate to admit it, mostly because i have hardly ever written code in such an organise way, but there really is something good about writting modular code, with each module carring out a simple task that can simply be simulated without getting lost in an overwhelming amount of information.
And so after a little battle with a few short circuits and double checking pin assiments i give you...
Lattice zx81.
Excellent well done.
Pictures of my tv never come out very good, but i assure you it's a good stable clear picture
I can believe it, my design with the Xilinx chip actually produces a much crisper picture, well using the transistor & 2 risistors composite mod anyways.
This is just a plain vanilla implementation at the moment, now i start working on the bells and whistles code
First thing clock doubling. @Prime... Did you ever get your clock doubling working ?
Nope scoping the outputs (with my logic probe) I couldn't see why it wouldn't work, clock outputs all looked good, switchovers from one clock to another where glitch free, it just didn't work
As I had been getting nowhere for a week, I decided to work on something else for a few days, and come back to it later so that I came back fresh.
I did get the screen inversion and key-reading going, and see no reason why the m1-not mod would not work.
oh and i need to tweak the Tape-in resistor network.
Yes, I came to the conclusion that I might need a small transistor amp, I found that some tapes loaded fine but that others didn't provide enough signal even with the volume on my tape deck turned all the way up
same tapes loaded absolutely ok on the same machine with the original ULA. Using Charlie's ZXpand I don't have this problem tho......
Out of interest how many macrocells does your chip have and how many is your design currently using, obviously I realise that this may not be directly comarible to the Xilinx chip, but I would imagine would be in the same ballpark.
For reffreence I'm currently using an XC95108 (108 macrocells), and the design is using about 75 of those cells.
Cheers.
Phill.
and built this...
)