RAM at 8-12, EEProm at 12-16k
RAM at 8-12, EEProm at 12-16k
I'd like to make a board like this.
Anyone done anything similar?
Cheers!
Anyone done anything similar?
Cheers!
Re: RAM at 8-12, EEProm at 12-16k
Decoding using 2 chips, use 2732 and 2 off 6116 or similar. just knocked it up off the top of my head...(spotted 1 mistake already need a signal diode between the edge connectors /ROMCS and the output of the INVERTER !) rush rush rush.....
http://i243.photobucket.com/albums/ff60 ... romram.jpg
regards Andy
P.S. what Ram chip did you want to use ? could be done differently for different ram chips.
http://i243.photobucket.com/albums/ff60 ... romram.jpg
regards Andy
P.S. what Ram chip did you want to use ? could be done differently for different ram chips.
what's that Smell.... smells like fresh flux and solder fumes...
Re: RAM at 8-12, EEProm at 12-16k
Nice!
I was thinking on my cycle ride home (in the rain) about a 'zeddie simulator'.
This week I've been trying to program some eeproms that I've pulled from some old PC motherboards - 29ee010/020 units. I've hooked them up to an arduino and an i2c I/O expander and tried to read from them. I'm getting really funky results and I want now just to hook it up to a 'proper' address/data bus and see if it works any better. Now then i thought - I'll put it on a zeddie! Hmm - but I need decode logic - and - well, that's just a _tiny_ bit beyond me. But what if I had a way of simulating it?
Well that got me to thinking - Arduino driving a pair of Max6965 i2c IO expanders into an edge connector. A zeddie simulator. You could effectively 'script' the changes in the signal lines and watch the results on the prototype logic you've dangled off it. Are you with me so far?
Arduino (or similar) -> IO expanders -> Edge connector -> ... >--Prototype board.
The thing about this is that you don't need a big fat wide logic analyzer or oscilloscope. You could clock the 'fake zeddy' real slow and probe the prototype logic at your leisure
Is that a good idea or is it the merlot talkin'?!
I thought about writing this in software. That's a bigger picture though.
C
I was thinking on my cycle ride home (in the rain) about a 'zeddie simulator'.
This week I've been trying to program some eeproms that I've pulled from some old PC motherboards - 29ee010/020 units. I've hooked them up to an arduino and an i2c I/O expander and tried to read from them. I'm getting really funky results and I want now just to hook it up to a 'proper' address/data bus and see if it works any better. Now then i thought - I'll put it on a zeddie! Hmm - but I need decode logic - and - well, that's just a _tiny_ bit beyond me. But what if I had a way of simulating it?
Well that got me to thinking - Arduino driving a pair of Max6965 i2c IO expanders into an edge connector. A zeddie simulator. You could effectively 'script' the changes in the signal lines and watch the results on the prototype logic you've dangled off it. Are you with me so far?
Arduino (or similar) -> IO expanders -> Edge connector -> ... >--Prototype board.
The thing about this is that you don't need a big fat wide logic analyzer or oscilloscope. You could clock the 'fake zeddy' real slow and probe the prototype logic at your leisure
Is that a good idea or is it the merlot talkin'?!
I thought about writing this in software. That's a bigger picture though.
C
Re: RAM at 8-12, EEProm at 12-16k
LOL i'm such a dummy ! never even considered /MemReq or /Refresh !
Going bed to get some rest and will draw better hopefully correct circuit tommorow
Andy
Going bed to get some rest and will draw better hopefully correct circuit tommorow
Andy
what's that Smell.... smells like fresh flux and solder fumes...
Re: RAM at 8-12, EEProm at 12-16k
Forget /refresh - static ram only please!
Andy - please see new subject in enulators topic about hardware simulator. It might be up your street.
Andy - please see new subject in enulators topic about hardware simulator. It might be up your street.
Re: RAM at 8-12, EEProm at 12-16k
Okay dokay
here is 1 chip version ! uses a few other components as well,
Regards Andy
here is 1 chip version ! uses a few other components as well,
Regards Andy
what's that Smell.... smells like fresh flux and solder fumes...
Re: RAM at 8-12, EEProm at 12-16k
Gorgeous!
I love the transistor-inverter!
I love the transistor-inverter!
Re: RAM at 8-12, EEProm at 12-16k
/MREQ should be used to enable the 138. Otherwise there could be some glitches, while the address lines are setup. So I would swap /MREQ and A15.
Siggi
Siggi
My ZX81 web-server: online since 2007, running since dec. 2020 using ZeddyNet hardware
http://zx81.ddns.net/ZxTeaM
http://zx81.ddns.net/ZxTeaM
Re: RAM at 8-12, EEProm at 12-16k
Good Point.
Thanks Siggi
Regards Andy
Thanks Siggi
Regards Andy
what's that Smell.... smells like fresh flux and solder fumes...
Re: RAM at 8-12, EEProm at 12-16k
It's fair enough that we assume ram = ~rom, but I don't understand the actions of the transistor. It's operating on both the newram and newromcs lines at the same time?
C
C