Hello there, I'm in need of 65xx gurus...

I've tried to build a "plug&play" 40-pin W65C816S module for my Oric (the Oric is a 6502 home-computer from Tangerine), but unfortunately it doesn't seem to work, I guess I have some timing problems...

I started by comparing the pinouts of the old NMos 6502 and of the W65C816S, and it appeared the two biggest concerns were the multiplexed Bank/Data lines, and the clock signals.

On the Oric, the clock is built by a ULA (Uncommited Logic Array) : the 6502 is thus fed with a 1 MHz signal, but this clock has a 2/3 low period and a 1/3 high period (this allows the ULA to make two memory accesses during the low "half-period", and let the processor have one memory access during the high half-period). So I sent the clock (Phi0 input on the 6502 socket) through two LS04 inverters in order to build Phi2 for the whole system, and through a third one in order to build Phi1 (Phi1 is marginally used on the Oric, it only drives a GI AY-3-8912 PSG).

Is this acceptable ? I mean, the NMos 6502 builds non-overlapping Phi1 and Phi2 signals from the Phi0 input, and I am only deriving Phi2 from a slightly delayed Phi0...

Also, I attached a 74LS245 to the Bank/Data bus of the W65C816S. I wired it to side B, and connected side A to the 6502 socket, so that I could drive DIR with R/W. /OE is driven by an inverted Phi2.
I have absolutely no idea whether this is correct or not (on a timing issue)... Does this additional inverter introduce a nasty delay ?

In one word, what shall I do ?

TIA,

Fabrice

PS: Hello Mike
PS2: There are schematics of the Oric on http://oric.free.fr/hardware.html

Can you get your hands on a 65802? It is an 816 but pin compatible with the 6502. A *REAL* plug and play.... (iunlike the MicroSloth version which is actually plug and PRAY...)

_________________
"My biggest dream in life? Building black plywood Habitrails"

I would love too...
In the past few years, I sent several mails to WDC... never got any answer. And then, the 65802 even disappeared from WDC web site...
So, I took the chance to have several W65C816S when Mike kindly organised the second bulk order... (the 816 is still great for its larger address space).
But, if you know where I can get one or two 65802, THAT would be a very nice Christmas gift

Merry Christmas to all 65xx users !!

Fabrice

Hi Fabrice,


You might find this article by Ruud Baltissen helpful: http://home.hccnet.nl/g.baltissen/02to816.htm


Happy Holidays!

Regards,
Mike

_________________
- Mike Naberezny (mike@naberezny.com) http://6502.org

Thanks Mike, I've given it an eye...
Unfortunately, I have the additionnal problem the processor is not allowed to use the data bus during the first half of Phi2...

Anyway, I have to rectify my first post...
I have just tried the module on a simple Oric-1 and it works !!
(I was initially trying it on an Oric Stratos/Telestrat)

So, I have to investigate why it works in a simpler machine and not in a bigger one : this shouldn't be a timing problem, after all ... (?)

In the mean time,

Happy new year !!!

Fabrice

???

Now it works in the Oric Stratos/Telestrat too...
I have absolutely not changed the wiring at all...
Well, the only change I've made is replacing the 70 ns ram of the machine back to the normal 150 ns...
Or maybe the 65816 module was physically pushing the right cartridge, making a bad contact in the PCB connector...

Ok, so, sorry for bothering the whole forum for a false problem, and thanks again to Garth and all of you, I will surely need you again

(next step is to find a way to raise the clock frequency of the 65816, and still have the rest of the system running at 1 MHz...)

Cheers to all,

Fabrice

Since several have shown an interest in the no-longer-available 65802, maybe someone could get some boards made to adapt an '816 to an '02 socket. Fabrice put a 74LS04 (although I would recommend HC or HCT) on his to take care of the clock differences, as well as a '244 so he could avoid bus contention by keeping the '816 from putting data on the bus during phase 1 when other things in his computer were using it. The '244 could be an assembly option, but making room for all of these in a package that's truly the size of a 40-pin DIP might require using the '816 in a PQFP. (These are actually quite easy to solder by hand.)

I've designed dozens of very dense multilayer boards for production, but feel rather unfamiliar with doing business with these prototype houses like Daryl used for his SBC that several here on the forum have. Our board manufacture is in a different league and first article usually costs a couple thousand dollars. Eventually I suppose I'll have to dive in-- but for now, maybe Daryl?? How 'bout it? Then your board could handle either processor!

I'd be happy to help. If someone can post a schematic that everyone agrees is acceptable, I'll create the board. The schematic can be in any format, as long as its readable.

I'll read over the tech docs and see if I can come up with a schematic as well.

Happy New Year!

Daryl

By the way, for those of you gurus who used Express PCB.com, their software just got upgraded to handle 4 layer board layouts. Cant wait to go to town with that puppy!

_________________
"My biggest dream in life? Building black plywood Habitrails"

I agree. However, the inner two layers can only be use as a power and ground plane. Data signals must still be on the outer layers. Still, it is a definite improvement. Now, all they need is an autorouter and they will have one great tool!

Daryl

Ok. First try at a schematic. Look it over and lets perfect it.

http://sbc.rictor.org/support/conv.html

(You may have to right click and select "save as" to view it)

Daryl

That would be great ! The physical height of the module might be of importance, too (I cannot close my Oric-1 anymore when my prototype module is inserted)...



Is there some access limitation ? I can only see a "Hosted by tripod" image (?)

Best regards to all,

Fabrice

Sorry about the previous link. I was in a hurry to get home from work. Here is an HTML doc with the picture included. It should work.

http://sbc.rictor.org/support/conv.html

Thanks!

Daryl

It looks great !
I have two questions, though...
- is there a reason why you send Phi0 to Phi2 ? I would have expected the 65816 to be clocked by the same Phi2 that is going to clock the whole system (the one coming out of pin 3 of the HC08). This is just a question so that I can better understand, I'm no expert...
- could you add a HC245 on the data lines (maybe in an optional form, as Garth suggested) so that the two data buses are separated when Phi2 is low ?

Thanks for the schematics !

Fabrice

No trouble. Now we need more feedback for additions and changes. How about it?

Daryl