Very simple IO board
Very simple IO board
Hi all,
Would it be of interest if I were to write a simple 'how-to' for those of you who are happy to solder a few wires? It would require just 2 or 3 chips, a prototype board and a zeddy edge connector.
The IO board would have 8 lines in each direction and this would be the 1st step to adding flash memory in the form of MMC cards to the zeddy...
If there was sufficient interest I might consider putting together a kit of parts for cost price + postage. You would need to be able to solder though - there's no way around this
Charlie
Would it be of interest if I were to write a simple 'how-to' for those of you who are happy to solder a few wires? It would require just 2 or 3 chips, a prototype board and a zeddy edge connector.
The IO board would have 8 lines in each direction and this would be the 1st step to adding flash memory in the form of MMC cards to the zeddy...
If there was sufficient interest I might consider putting together a kit of parts for cost price + postage. You would need to be able to solder though - there's no way around this
Charlie
Re: Very simple IO board
I can also probably help in that if any hardware projects get off the ground and there is enough interest, I have found a good electronics engineer, who can help design, prototype and build finished products which I can then offer for sale via my website.
Rich Mellor
RWAP Software
RWAP Adventures
SellMyRetro
Retro-Printer Module
Also Involved in:
Icephorm
RWAP Software
RWAP Adventures
SellMyRetro
Retro-Printer Module
Also Involved in:
Icephorm
Re: Very simple IO board
as i posted earlier today i designed and built a simple IO for ZX81 using just 3 IC's A 74ls32 , A 74ls273, and a 74ls245.
http://homepage.ntlworld.com/deborah.cl ... zxio-b.jpg
that image shows the output(top ic 74ls273), connected to the inputs (bottom ic 74ls245) making it a psuedo 8 bit bi-directional bus (either end can drive a line low, but not force it high) but if you didn't connect the inputs to the outputs in such a way and remove the diodes you'd have 8 outputs and 8 inputs with which your free to do whatever you liked.
A6 on the zx81 edge connector needs to by low i used port $BF as this didn't collide with anything else i was already using.
Andy
http://homepage.ntlworld.com/deborah.cl ... zxio-b.jpg
that image shows the output(top ic 74ls273), connected to the inputs (bottom ic 74ls245) making it a psuedo 8 bit bi-directional bus (either end can drive a line low, but not force it high) but if you didn't connect the inputs to the outputs in such a way and remove the diodes you'd have 8 outputs and 8 inputs with which your free to do whatever you liked.
A6 on the zx81 edge connector needs to by low i used port $BF as this didn't collide with anything else i was already using.
Andy
what's that Smell.... smells like fresh flux and solder fumes...
Re: Very simple IO board
Well seeing as you showed me yours...
This is addressed at port 7 for in, and port 17 for out.
4 chips, though..!
This is addressed at port 7 for in, and port 17 for out.
4 chips, though..!
Re: Very simple IO board
more chips equals more functionallity, it's a more elegant decoding scheme for sure. Nice one Sir Morris.
Regards Andy
Regards Andy
what's that Smell.... smells like fresh flux and solder fumes...
Re: Very simple IO board
Ahem I must admit I didn't invent the decode scheme - It came from a board by one of the zx-team via Siggi!
The input isn't latched either, there was a reason I'm sure but the mists of time have passed over me since I did it
The input isn't latched either, there was a reason I'm sure but the mists of time have passed over me since I did it
Re: Very simple IO board
Xavier ...on the Facebook groupe : "Zx81 France"(fr)
Re: Very simple IO board
Xav - is your board is memory-mapped in the 8-16k area? And is it output only?
It looks like you make your own PCBs too - I haven't tried this yet though I think I might have a go. It's the investment in chemicals and the rest of the kit that puts me off..
It looks like you make your own PCBs too - I haven't tried this yet though I think I might have a go. It's the investment in chemicals and the rest of the kit that puts me off..
Re: Very simple IO board
HI,
Output only if used on the ROM, but in top memory input can can be available ? (Rom mirroring?)
It can be mapped on the ROM or in unused memory segments! (Poke 7777,0 is an exemple)Xav - is your board is memory-mapped in the 8-16k area? And is it output only?
Output only if used on the ROM, but in top memory input can can be available ? (Rom mirroring?)
True!It looks like you make your own PCBs too - I haven't tried this yet though I think I might have a go. It's the investment in chemicals and the rest of the kit that puts me off..
Xavier ...on the Facebook groupe : "Zx81 France"(fr)