Hi Michael,

You obviously seem to have gone much further than I have wrt to pics and external control. I must admit I have not played with any fast pics .. Best I had was a 40Mhz 18f4550 chip ..and I don't think I ever ran it that fast ..mainly 20Mhz

Anyway great in what you are doing ..I'd be very much interested in any outcomes you are willing to share .... I mainly play around with pic basic pro and pics .. but I assume in what you are doing ..you might be dealing at assembly level programming ..which is not that scary ..if it is small type programs ..once it goes over a page or so ..I usually give up.. and try to look at an easier way of doing things..

I actually set out once to use an external NVram and DMA contol it between the pic and an old micro (like say a 6502) ..i,e use pic to pre load the ram/ed\it etc ..once all there.. transfer the Nvram to micro to run .. in that case you would not need super fast pic .. and could do all the control even through pic basic .. I sort of started that ..but got carried away with other stuff

Meantime I've seen people use pld's and I had to have a go with them.. they are easy to implement (could be horrable to program..but for simple stuff like cobinatorial logic ..it is easy .. once you get hang of it..

As far as price .. they are not that expensive (even compared to pics) about $5 for 22V10 24 pin chip.. has 22pins to play with..


programming them yes that can be an issue .. I ended up buying Wellon 290 programmer that can do them (about $150) .. but I believe G540 which is about half price will do them too. Best suggestion I can make about programmers and pld's ..is make sure the programmer can support it and see if someone has already used them for that chip ..since some manufacturers claim support for lot of chip .. but some of them just do not work...

All the best

mc

https://sites.google.com/site/gogleoops/

I appreciate all the info, Bill. Thank you.

I've often wondered if something like Daryl's "DEC-1" decoder could be modified to produce a /RAM select for everywhere outside of I/O space located in zero page. That is, could it be made to produce four I/O chip select outputs in the range of $0080-00BF, for example, and a single RAM chip select output for $0000-007F & $00C0-FFFF? I wouldn't need a ROM select output but I would need something like an "enable" input to turn the decoder on or off during PIC "blind loader" or "blind monitor" operations when the PIC needs to push/pull instructions and data to/from the CPU over the data bus from outside of 6502 address space.

It sounds like you've got all the resources needed to take advantage of GAL logic. Very cool!

BTW, the Atmel AVR microcontrollers and devices seem pretty neat. I've just never had an opportunity to try them out.

Cheerful regards, Mike

Hi mc (chessdoger),

May I ask if there's a way to add the missing "single-step" feature to your mini SYM-1 design, please? Perhaps by modifying the GAL logic? After taking a peek at the SYM-1 documentation, this seems like a "must have" feature, even for a reduced-feature mini system.

Cheerful regards, Mike

Hi I assume you are asking about debug feature ... I did not connect the debug buttons as such as they involved using another PIA (6522) chip .. unless you are keen on redirecting everything through 6532 and re editing the monitor.. which sort of makes it nonstandard then.. I also had looked at redirecting the cassette tape input to the 6532 ..and not have it through another PIA .. but thinking about it .. if you can load and save though a terminal program .. somehow..is just as easy through the terminal ....as having to add extra circuit to save to audio and back .. so put that on back burner for now..

I assumed the Debug on/off push buttons and few surrounding gates of U7 and U8 that route the SYNC signal to the NMI pin were all that was necessary to support single-step operation.

Please forgive me. My question was premature. I'll continue reading the documentation.

Cheerful regards, Mike

Hi mc (chessdoger),

I found a better schematic segment in Figure 4-6 on page 4-19 of the SYM Reference Manual that shows the connection between 6522 VIA #3 (U29) and the "debug" hardware (excerpt below). Thank you for pointing out the dependency. It seems VIA #3 outputs PA4 (labeled "DON") and PA5 (labeled "DOF") provide SUPERMON with a way to turn "debug" on and off. Is that correct?

Back to my research.

Cheerful regards, Mike

That should be very possible.

_________________
Bill

Very cool... I'd love to see what the GAL program would look like for that!

Regards, Mike

Hi Mike (chessdoger),

While I continue to read and soak up SYM-1 documentation, could I take advantage of your SYM-1 knowledge and experience, please?

Is there a CRT mode command to turn Debug mode on and off when running in a terminal session via the CRT (serial) interface or do you still have to toggle Debug mode on and off using the push buttons on the keypad? I realize you could probably just call the DBON (80E4) and DBOFF (80D3) subroutines using the 'Go' command but are there dedicated CRT mode commands for toggling Debug mode on and off that I haven't come across yet in the documentation?

How familiar are you with the SuperMon monitor? Are the 6522 VIA#3 (U29) PA4 ('DON') and PA5 ('DOF') connections to the Debug circuit flip-flop just used for the Trace portion of the Debug feature? IOW, does the single-step portion of the Debug feature also rely on 6522 VIA#3 'DON' and 'DOFF' signals? I can't quite tell by looking at SuperMon (yet).

TIA... Regards, Mike

Added: While reading the SYM-1 Reference Manual I came across text on page 9-14 that says you have to press the Debug ON push button on the keypad before pressing G and <cr> in order to continue single-stepping through a program. Does this match your experience using the SYM-1?

have few more boards now ..still have z80 board to come and few more 6502 boards

https://sites.google.com/site/gogleoops/home