W65C02S, Z80, 80C31 or other legacy processor?

Consider extending your definition of "macroscopic" down to SO packages. I personally find 50 mil pitch surface mount to be quicker to hand solder than DIPs. Or is the concern that you want something that can be socketed for when the students let the smoke out?

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Rob Gaddi, Highland Technology
Email address is currently out of order

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Obviously you want a fully static design so you can step it cycle by cycle and/or insruction by instruction. Also, it would probably be good to have tons of legacy software, such as debuggers, monitors, assemblers. For those reasons, I suggest Z80 and making the computer compatible either to CP/M 80 or ZX Spectrum.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Socketing is the issue, not so much for the magic smoke as for plugging in daughterboards underneath the chip (not the way I wanted t do it, but not my choice, and yes I know there are other ways of doing daughterboards if daughterboards it must be).

I personally have no problem with SOIC gull-wing, and little problem even with TQFP and TSSOP (under magnification). Some parts of the board will use SOIC glue logic.

Yes, that's true...

Not a major criterion for this application, and no native development tools will be necessary on the device except the HLL I'm writing, and a very simple monitor - for which I have many possible choices. I can't see a CP/M machine with only 8K of ROM and 8K of RAM, anyway. And I'm certainly not going to try and emulate all the goodies in a Spectrum's ULA, the display interface on this device is specified as 7- seg LEDs and a small text LCD.

Perhaps the easiest solution would be the EMULATION of the hardware of either one of the legacy processors by means of the modern processor like AVR. You can select whatever architecture you like or even invent a CPU of your own, you have a lot of useful stuff on chip to assist the development.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Would something like these be acceptable? It certainly opens up the possibilities for more modern processors:

I suspect you can find lots of vendors making adapters like those.

Also, some of the starterkits have headers with external busses:

The left board is the starterkit, if you put in a 3x32 header you could plug wires into it, or build a custom right-side board to break out the specific signals you want in some convenient format.

larwe schrieb:

This seems to be a good starting point, and eol parts won't be a problem for you.

Otherwise, digikey still sells the 68k, which is an extremely good teaching platform due to its easy assembler language.

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Mit freundlichen Grüßen

Frank-Christian Krügel

I have boxes of ancient (and working) 80C31's sitting on a shelf. (Not that it matters to this question.) But you can get the AT89 from Atmel and the C8051F from SiLabs. Both companies make them with external bus capability, I believe.

I like the 65SC02 and WDC licenses the core in a variety of already done ASICs as well as in synthesizable form, I think. So that's a good choice, too.

Jon

I have a strong leaning to use the 6502, for other reasons. Do you happen to know the answer to my question about whether a design can be made to accept both regular 6502 and W65C02 as drop-in substitutes?

At a very quick glance it seems that at most I might need an external jumper, but if anyone has actually tried this...?

Not a bad idea, I am looking at how close I can make it "look" like a normal CPU from the outside by simulating the address/data buses and control signals in software on say an ATmega32.

Yes the 65C02 and 6502 are pin compatible, or at least a 65C02 could be placed in a properly designed 6502 socket without jumpers. Was done by some Apple ][+ users. And if I recall correctly the Apple //e shipped with 6502 but when the Apple //c came out with a 65C02 there was an inexpensive firmware and CPU kit from Apple to upgrade the //e to "//e enhanced" to be more like the //c.

There were some non-compatible pinouts such as the 65C102. The C102 might work in an Apple because Apple didn't use the CPU to oscillate the clock crystal.

The 65C802 was a 16 bit upgrade which ran in the same 65C02 socket. Apple //gs used 65C816 with a different pinout.

These days stuff you need you may find in a niche computing (but not too-obscured) cyber-scene called "retroputing". Google it a bit and you will find a bunch of stuff.

Z80 and 65C02 and 80C31 still live today but in another realm of existance (as IP cores, see

and many commercial firm in 'IP Core' business) or as a part of SoC designs or in some another form of larger design where syntesizable version of their respectable instruction set are modeled in hardware-description languages (typically VHDL and/or Verilog). For example Don't expect pin-compatible chips being manufactured these days. Z80/65C02/C31 are history and should remain there.

What you actually need is called "a trainer" (or, IMHO, more appropriate term would be SBC - "a single board computer" for educational purpose).

New CPU players are in the game since long time ago - you may reconsider building your trainer with, let's say, Atmel ATmega128 series of chips, architecture with quite enough space for your need.

Meanwhile, let's say you want to stick with the first CPU of your choice (W65C02S). You may actually find real CPUs on myrad of B2B (business-to-business a.k.a. professional auction sites, for example

sites to buy in quantities and many "hard-to-find-component" sellers will be more than glad to sell you an "old-new-stacks" of long-time-ago-warehoused-and-ever-since-dust-collecting components. Another source is, of course, the eBay.

Many enthusiasts (a.k.a "old hands", oldtimers and retroputing-lovers) are maintaining quite extensive sites, like

There you may find a *load* of stuff. For example, you may find a complete KIM-1 early development system, a working replica, with all the details you may ever need, for example the source code of the ROM. KIM-1 enthusists have their own page (Nice pics here:

There is a lot of retroputing stuff outthere .... just too much for a single post ... ... just to keep you going, for example, by reading this blog you'll digg out an actual working 6502 BASIC interpreter "allegedly" written by Bill Gates/Steve Wozniak

which can be 'probably without too much problems' adopted for your needs ... ;-)

Akin to 6502 and respectable 6502.org pages are:

- Z80:

- 80C31:

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StoneThrower
www.dgmicrosys.com

If you head toward the z80, you might shift to the 8080. The z80 is basically that with additions - same machine code not counting the additions. The question of why such a machine is a bit of a mystery - could you disclose the purpose?

Hul

snipped-for-privacy@gmail.com wrote:

I sure liked my RCA (now Intersil, I think) 1802. Dunno if it is still around, but for quite a while it was the defacto standard for 8-bits in space, due to it's HUGE geometry making it bullet (and cosmic ray) proof.

Easy, orthogonal instruction set, DMA hardware that could be used to toggle in programs by hand, works from 5V to 15 -- what more could you want?

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I'm very aware of it, since I am a significant collector, lover and user of ancient machinery - my next book is being written on a (physical) Apple IIc in fact, though I am being exhorted to do it on a IIgs :) see the skeleton of my museum at .

In fact I had originally written in my post "think of this project as something like a KIM-1". That should put me in context for you :)

Anyway, the design intent of this appliance abhors emulation. To put it in retrocomputing terms - this is a "replica I" (made from original components), not a "C64 DTV" (simulated in an FPGA/ASIC). Although it is in fact neither of these things. I am under NDA for the exact details of it, at least for the moment - that will likely be lifted soon.

Not yet, sorry - except to say that it is educational, and aimed at the school grades 6-9 age bracket.

They might still make the sapphire spacecraft versions of the ol' Cosmac but the regular versions are out of production. A few retrocomputing projects that use it have apparently bought most of the remaining stock.

I had a 1802-based CHIP-8 SBC back in my misspent youth, I agree it would be a good choice but is now unobtainium :)

The ability to buy it ex stock until December 2014 :P

I would recommend the Z80. It is simple, representative of modern systems, and available in various forms. The Z180 (or 64180) is probably the handiest, since it includes an adequate selection of peripherals in 64 pin DIP. Yet memory is external (up to 1 Meg.) and so can be 'blinkenlit'. You have various OS's available for it (see DOSPLUS v 2.5 on my pages) with full source. You can create an interesting system by designing a single external memory based display page, and a display mechanism, if you want to avoid an external terminal. Another exercise might be to adapt a common IBM PC keyboard.

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 [mail]: Chuck F (cbfalconer at maineline dot net) 
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"Tim Wescott" ...

AFAIR, I wanted a stack pointer. Wasn't the 1802 the chip with just a link register that held the interrupt and call return address?

It was perfect for portable stuff because of its low energy consumption, I designed a time registration system with it. Pity we had no LCD back then.

Regards, Arie de Muynck