Hi guys,

I'm working on a 3d animation of the 6502 internals, (using Blender).

It's going to be a "metaphoric" explanation of how a processor works.

I.e. I have animated characters representing computer bits, and other animated characters for electrons.

I'd like to model the reset logic as accurately as possible, but I have no idea of how the 6502 does that.

For my simulation, I'd like to model right down to the internal operations of capacitors / transistors etc

I have novice level knowledge of electronics, but feel free to get as detailed and technical as you like , and I'll try to "keep up".

Thanks in advance for any info . ... links etc.

I'll post a W.I.P, if anyone is interested.

Mike

Hi Mike
an excellent idea!

This article on pagetable is good for the logical level, and this wiki page section ("masking of the stack writes during RESET") on visual6502.org points you to a transistor-level simulation of the reset sequence. (Click on 'Show Chip Layout' for the visuals) For further specifics, please ask away!

Are you animating the 6502 masks, like the visual 6502, or something more like Hanson's Block Diagram?

Cheers
Ed

Hi Ed,

Great Stuff !!

Thanks very much !

That http://visual6502.org/JSSim/expert.html is incredible !

Do you know if the DSH -> VHDL code is online ?


>Are you animating the 6502 masks, like the visual 6502, or something more like Hanson's Block Diagram?

Heh, my animation is direly lacking in realistic details, that's why I posted here

More like the block diagram at the moment, but I'd like to get something somewhere in between those extremes of detail

Mike

Hi Mike
Well, I've never yet seen or found the DSH converter code - it might be out there somewhere. Likewise the referenced report is 118 pages, and I haven't seen that (perhaps the report includes the source?)

Cheers
Ed

Ed,

Ok, thx.

Getting back to the reset :

Is the nodenames[res:159], the pad that an external reset switch would be connected to ?

If so, it seems that it's active low.

Would the reset switch then be a type of switch that is normally closed, and then opened when pressed ?

Mike

Connecting the switch directly to the RST\ input is ok on the CMOS 6502 (65c02) with an RC time constant on it because it has a Schmitt-trigger input. On the NMOS 6502, the RST\ pulse must be debounced and timed. The timer part is necessary because holding the RST\ input low for more than 50 or 100ms causes heating problems and malfunction. This again is on the NMOS 6502. It's not a problem on the CMOS 6502. On both however, it is active low.

Hi Garth,

Do you know if the CBM had some sort of reset circuit like this : (I realize this is for the disk drive) :
http://www.unusedino.de/ec64/technical/ ... ml/06.html

...or just a "debounce" circuit, as you mentioned?

(Did the CBM have the "older" / debounce required chip ?

Any links or info to the debounce circuit would also be great

thx

Mike

Mike, the C64 used a 555 timer for RST\ (actually half a 556 timer IC). It did not have a reset button which was kind of an irritation, so when I made an interface board, I added a reset button and circuit which works more like the one you showed. You can see it here. I normally use a Schmitt-trigger IC like the 74HC14 (yours shows the 74LS14), but here I made one from a couple of available sections of a 74HC00. In case it's hard to read the values, they are, from left to right, and top to bottom: 2.2K, 47uF, 470, 2.2K, 1uF, 8.2K, 33K, 4.7K, 22pF, 2N4401. I wish I had documented it better. It seems a bit odd right now, but it did work just fine. Since the C64 already had a reset circuit for power-up, this one only had to do its job with the button. I don't work with the NMOS 6502 but in this case the C64 has one and there's no getting around it. The reset circuit for the CMOS 6502 (actually 65802) on my workbench computer is shown here, again making use of a section of an IC that was there for other things, the 74HC14 (now 74AC14). It does not limit the length of the pulse since that's not necessary on the CMOS 6502. The info on the workbench computer there is quite outdated (because I have added a lot since that was posted), but go ahead and see the different parts of it at the various links.

Heh ... I've been sidetracked for awhile, but I haven't forgotten about this project.

I'm still exploring the reset logic "path", but another fundamental thing I'm interested in is the clock circuit / generator.

I'm particularly interested in finding out about the CBM clock circuit, but any info is as always appreciated.

Is it some sort of square wave oscillator circuit ?

If so, I've found lots of examples, but I'm interested in the "authentic" / original design

Mike