Building a simple 6502 microcomputer

[BigEd]

I'm sure you don't aim to discourage anyone, but you know how I feel when I see a barrage(*) of minor corrections piled onto a beginner. I know that you feel differently about that - I'm not expecting you to change, but I feel it worthwhile to provide a balancing view.

I feel sure we used to be able to make those correcting points more deftly and with more encouragement.

Cheers
Ed
(*) it seems to me like a barrage. The new visitor may see it only once, the rest of us see it every time.

[GARTHWILSON]

We all want the newcomer to be as successful as possible, and the CMOS processor will contribute toward that, although admittedly other factors will have even more effect. If it were me, I'd want to absorb all the info I could, trying to ride the peak of the curve between hungering for more info and OTOH getting overloaded.

[alkopop79]

Love the enthusiasm and passion here. Will write an introduction!

[alkopop79]

Dajgoro wrote:

Edit: alkopop79 have you looked at the SBC-2 schematic? I used it as a base for my sbc.

Yes! It seems viable, could try it WW.

[alkopop79]

Dajgoro wrote:

alkopop79 wrote:

Just purchased a 6502 from ebay! Happy times!

I have a stack of 65xx, ram , rom an other stuff that BitWise sent me for free, so if you need some ic, just send me a pm. Check on this topic.

Thanks! Luckily I live by one of the very few component suppliers in London. At least they stock the TTL logic ICs.

[BigDumbDinosaur]

alkopop79 wrote:

Dajgoro wrote:

alkopop79 wrote:

Just purchased a 6502 from ebay! Happy times!

I have a stack of 65xx, ram , rom an other stuff that BitWise sent me for free, so if you need some ic, just send me a pm. Check on this topic.

Thanks! Luckily I live by one of the very few component suppliers in London. At least they stock the TTL logic ICs.

If they have the 74AC or 74HC logic series, you might wish to build with it instead of 74LS. Also, when you go shopping for parts don't forget that there are a number components vendors on-line that may offer more selection and more favorable pricing. A least two in the USA can supply purchasers in the UK at reasonable prices—Digi-Key being one such company. Shipping isn't as onerous as it was in the past, but there's no escaping the VAT. UK forum members like BigEd and leeeeee can probably advise you on getting the most for your money when buying parts.

[fachat]

If you're going 74AC or 74HC make sure, your design is all-CMOS. TTL (like non-CMOS 6502, or plain LS) outputs need ACT or HCT inputs.

André

Edit: _TTL_ outputs like non-CMOS 6502 or plain LS.

[BigDumbDinosaur]

fachat wrote:

If you're going 74AC or 74HC make sure, your design is all-CMOS. TTL (like non-CMOS 6502, or plain LS) outputs need ACT or HCT inputs.

André

Edit: _TTL_ outputs like non-CMOS 6502 or plain LS.

Right...thanks for highlighting that. I occasionally forget to mention the CMOS/TTL thingie. It's part of why I keep recommending that new builders stay away from the NMOS parts if at all possible.

[alkopop79]

Torn between the SBC-2 and the UK101. In the meantime generate some clock with a crystal/555/microcontroller and poke around on the breadboard with an oscilloscope. Would like to wire wrap the SBC.

[BigDumbDinosaur]

alkopop79 wrote:

In the meantime generate some clock with a crystal/555/microcontroller and poke around on the breadboard with an oscilloscope.

A can oscillator is all you need and is less trouble. Avoid making it complicated.

Quote:

Would like to wire wrap the SBC.

Good idea. Easy to fix mistakes and you should be able to get stable operation up to 4 MHz without too much trouble.

[alkopop79]

I reckon I can hook up my microcontroller dev board to the Rockwell processor and 'fake' instructions. Both the SBC-2 and the UK101 lack keyboard and display. I wonder if it's possible to hook up a hex keypad and an LCD display to both? I just don't fancy the idea of having to use a 10000x times more powerful laptop to be able to use the SBC. Also, found a cheap (approx. £18) Willem burner, made in Canada on Ebay.

[alkopop79]

Just found an article about how to program EEPROMs manually. I also saw a DIY circuit somewhere for this task. What's your angle on this guys? EEPROM or EPROM?

[alkopop79]

This EEPROM burner looks great and would be a good start to learn WW. Again, loved to hear your opinion!

[BigDumbDinosaur]

alkopop79 wrote:

Just found an article about how to program EEPROMs manually. I also saw a DIY circuit somewhere for this task. What's your angle on this guys? EEPROM or EPROM?

EEPROMs are usually more convenient with which to work. If you decide instead to use EPROMs you'll need to come up with some means of erasing them.

[Dajgoro]

alkopop79 wrote:

I reckon I can hook up my microcontroller dev board to the Rockwell processor and 'fake' instructions. Both the SBC-2 and the UK101 lack keyboard and display. I wonder if it's possible to hook up a hex keypad and an LCD display to both? I just don't fancy the idea of having to use a 10000x times more powerful laptop to be able to use the SBC. Also, found a cheap (approx. £18) Willem burner, made in Canada on Ebay.

I made myself a interface for that. I took a pic16f877, and i used the parallel slave port, and when the cpu writes a byte to it, the mcu displays it on the lcd display(with the regular Hitachi controller), and when the cpu reads the mcu it outputs the pressed key on a ps/2 keyboard. The only tricky part is that you can't read or write data in a thigh loop, because the mcu would get too much interrupts, and it couldn't handle then all on time, so i just added nop instructions after every read/write to the mcu port, and it works perfectly. I never set the code for download, since i never finished the i2c part that is supposed to communicate to the rtc chip. If you want i can send you the code, source and hex, and just program the mcu with it and it works.
I also used it in my 68k sbc, and it works there too.