First 6502 project

BillO · Post by **BillO** » Fri Nov 20, 2009 11:57 pm

Rick Cortese wrote:

I think Pittman<?> put tiny basic in ~1800 bytes. For the 6502 it was something like 2,200 bytes which really hurt at the time: Needed 2 EPROMs.

Yes, I can see how the 1802 architecture could help with Tiny Basic. The original version for 6502 was meant to be loaded into ram on the KIM. I think the 6800 version just fits under the 2K limit.

spinnaker · Post by **spinnaker** » Sat Nov 21, 2009 12:41 am

BillO wrote:

Spinnaker:

Oh, please don't go the PIC route! They are soul-less products of modern engineering. There is no fun or enjoyment to be had using them. They are too easy and work too well.

Stick with the NMOS 6502. Seriously. I get that this is a hobby, right? Then there will be little fun is something like a PIC. Let that come later once you think of projects that may need multiple controllers or once you’ve had enough fun.

On the I/O, did you consider an ACIA? A KIM work-alike could easily be made using serial I/O. If you are dead keen on the HEX keypad, you might want to look into a 74C922. It will do all the decoding and de-bouncing for you in a single IC.

No I for sure want to build a KIM lookalike.

GARTHWILSON gave me a great lead on hex keyboards.

He said to use a smart display but since I want to create a look alike I think I will go with a seven segment display. Maybe they have cooler colors today? And I will go that route.

Any idea what I could use to encode the display for hex? I found a youtube vid where the guy used a GAL16V8.

Any other ideas?

8BIT · Post by **8BIT** » Sat Nov 21, 2009 1:06 am

spinnaker wrote:

Any idea what I could use to encode the display for hex? I found a youtube vid where the guy used a GAL16V8.

Any other ideas?

My 1802 ELF II computer used a 9368 IC to convert a 4 bit binary value to the 7 segment LED and displayed all 16 HEX characters.

I did a quick search. Try MD9368 or Fairchild 9368. Could also be 4368 but am not sure. It seems to be out of production but you may be able to find some.

Daryl

BillO · Post by **BillO** » Sat Nov 21, 2009 1:52 am

For the display you could use HP 5082-7340 or the like. Or even the newer ATMega8 (http://www.avrfreaks.net/modules/Freaks ... Driver.pdf)

Of course, the ATMega8 is based on an AVR chip that is light-years ahead of the 6502, but that's beside the point.

I used to use a 7 segment decoder-driver back in the late 70's. I'd swear they were TTL, but I can't find hide nor hair of them now. Maybe it was all the psychedelics…..

spinnaker · Post by **spinnaker** » Sat Nov 21, 2009 2:18 am

What are the RHD LHD designations on the displays mean?

Right hand display and left hand display? If so, what does that mean?

Some say right angle. Is this another way to say the same thing?

spinnaker · Post by **spinnaker** » Sat Nov 21, 2009 3:05 am

BillO wrote:

For the display you could use HP 5082-7340 or the like. Or even the newer ATMega8 (http://www.avrfreaks.net/modules/Freaks ... Driver.pdf)

Of course, the ATMega8 is based on an AVR chip that is light-years ahead of the 6502, but that's beside the point.

I used to use a 7 segment decoder-driver back in the late 70's. I'd swear they were TTL, but I can't find hide nor hair of them now. Maybe it was all the psychedelics…..

Yikes!!! $4.75 a piece

http://www.elexp.com/ics_10cn.htm

An AVR or pic to handle the display and I/O might be kind of interesting. Sort of old school / new school.

GARTHWILSON · Post by **GARTHWILSON** » Sat Nov 21, 2009 4:08 am

Quote:

What are the RHD LHD designations on the displays mean?

Probably right-hand decimal point and left-hand decimal point.

Quote:

Some say right angle. Is this another way to say the same thing?

Right angle usually means they stand up perpendicular to the board, so if you look at the board from the edge, the LEDs face you.

How did the KIM feed the display, and how close to the same do you want yours to be?

I will reiterate that the PICs, although they have a nice set of onboard features, have a really, really lousy processor. It was designed in about 1975 by General Instrument which later spun off the division. In spite of all of Microchip's bragging about their Harvard architecture, it typically takes a PIC16 twice as many instructions and twice as many clocks to do a job as a 65c02 takes, and four times the difficulty in thought process to program the solution because the PIC's instruction set is so weak. The fastest 65c02's are ten times the speed of the fastest PIC16's, and I don't know of any 8-bit processors that can touch the 65c02 in interrupt performance.

BillO · Post by **BillO** » Sat Nov 21, 2009 4:12 am

There is always the 4511 decoder-driver IC. This is a CMOS chip, but should suffice.

Really though, I'd look at using a 6551 (not everyone’s favourite) or 2651 ACIA (asynchronous communications interface adapter) as a way to hook the thing up to a PC as your terminal. That way you can develop and store programs on the PC and download them to your project. Taking this route you can avoid the hex keypad and display.

While not as authentic as the keypad and display, it is a much cheaper and simpler route.

I have no way of uploading documents to this site (clever move ... ah?) but if you have an e-mail address I can send you a sample project I did a while back that includes schematics, bios, language, etc…

BTW, there are nice and cheap EPROM programmers available on eBay. Just search for “Willem EPROM Programmer”. You should not have to pay more than about $40 to have one delivered. They work just fine.

spinnaker · Post by **spinnaker** » Sat Nov 21, 2009 4:27 am

BillO wrote:

There is always the 4511 decoder-driver IC. This is a CMOS chip, but should suffice.

Really though, I'd look at using a 6551 (not everyone’s favourite) or 2651 ACIA (asynchronous communications interface adapter) as a way to hook the thing up to a PC as your terminal. That way you can develop and store programs on the PC and download them to your project. Taking this route you can avoid the hex keypad and display.

While not as authentic as the keypad and display, it is a much cheaper and simpler route.

I have no way of uploading documents to this site (clever move ... ah?) but if you have an e-mail address I can send you a sample project I did a while back that includes schematics, bios, language, etc…

BTW, there are nice and cheap EPROM programmers available on eBay. Just search for “Willem EPROM Programmer”. You should not have to pay more than about $40 to have one delivered. They work just fine.

I have a small boat load of 6522s. Could I use those for my hex display?

But I don't want to give up the idea of using a PIC for my UI. Might be kind of interesting. The only thing I can't figure is how the PIC would be addressed by the CPU? The ones I looked at have no CS. Unless I would do it all through a I/O port like a 6522?

Will pm you with my email.

GARTHWILSON · Post by **GARTHWILSON** » Sat Nov 21, 2009 5:51 am

Quote:

I have a small boat load of 6522s. Could I use those for my hex display?

Sure. There are plenty of ways to do it, using anywhere from three I/O pins total (to feed external shift registers like the 74HCT595) up to one 6522 I/O pin for every segment.

Quote:

But I don't want to give up the idea of using a PIC for my UI. Might be kind of interesting. The only thing I can't figure is how the PIC would be addressed by the CPU? The ones I looked at have no CS. Unless I would do it all through a I/O port like a 6522?

Look up the Parallel Slave Port in the PIC data sheets. You can put it right on the processor's data bus, but it's slower than a 6522 because you have to for example write the data to the PIC, then give it enough time to see it and do something with that info, then come back again and tell it what it's supposed to do with that data, then again give it more time to process it, maybe polling it in between to see when it's ready for the next thing, and so on. If you want to read data, you'll tell it what you want to read, give it time to get that data ready to output, come back later to read it, etc.. (Edit, 10/19/18: Microchip's ap. note AN579, about using the PSP, is at http://ww1.microchip.com/downloads/en/A ... 00579b.pdf ). For this reason it would be better to use the PSP only if the amount of data is rather small compared to the job the PIC will be doing with it. Constantly strobing your LED display would be an example, where the 6502 can offload that continuous job so it doesn't have to babysit the display, or even look up what segments to light for each character. The PIC can take over that part, and you have essentially made an intelligent display module. You could make the PIC take on the job of flashing a digit to show where the cursor is, scroll the display, and other jobs.

Nightmaretony · Post by **Nightmaretony** » Sat Nov 21, 2009 3:58 pm

and if you prefer to simply address for your digit display, simply use 2 parallel ports such as 74LS374s and address them as individual locations. Use one for the segments drive and the other as the individual digits drive. This will give you an 8 digit display. This also has the advantage of a low cost popcorn chip costing oyu less than a 65C22, AND you can create a full shape table and do graphics on the display, which would be impossible with a dedicated segment decoder.

One nice advantage though it adds up as Garth mentioned would be using PICs or AVRs to do slave work such as I/O or video ops. I think Darryl's SBC2 uses that method with a 65C02 base and an AVR for video generation. It also forms a good learning tool for multiple processor platform in different language as well as how each processor talks to each other...

Rick Cortese · Post by **Rick Cortese** » Sun Nov 22, 2009 10:31 pm

IIF you mostly want to keep it period correct w/o going to the high priced solutions, go with an EPROM for display decoder. It will work with FND500's<?> and you just have to program the bit pattern. You just wire the data bit into the 7 segments i.e. address $00 of the EPROM outputs highs for segments ABCDEF to make a 0, address $0A outputs highs for ABCEFG for an upper case 'A.

I think most stuff from back then multiplexed displays so you would need the addition of something like a 74LS138 one of eight decoder to switch displays and the address data into the EPROM.

IMHO there is nothing wrong with your plan to implement something using the 6522. I think for a simple solution I might go with a RIOT chip if they can still be purchased. Plenty of I/O to do display decode and multiplexing and enough RAM to actually do something. Figure you are comitted to having some kind of ROM and need RAM just because it is a 6502. You can wire the RIOT to act as page zero, the stack, display multiplexer.

Rick

Nightmaretony · Post by **Nightmaretony** » Mon Nov 23, 2009 3:32 pm

RIOTs be fairly hard to get. 65C22 VIAs are much more common to get these days

PaulF · Post by **PaulF** » Mon Nov 30, 2009 4:59 pm

Quote:

What are the RHD LHD designations on the displays mean?

I remember seeing these on dual displays, when they stood for Right Hand Digit and Left Hand Digit.

HansO · Post by **HansO** » Tue Dec 01, 2009 10:59 am

spinnaker wrote:

I have a small boat load of 6522s. Could I use those for my hex display?

Yes you can. If you want the hex keyboard and the LED display you may ha ave a look at the KIM-1 design. The KIM-1 usies 6532, but nothing in the keyboard/display is special that you can also do with 6522. Simple and effective.