ACIA/UART (6551) current equivalent

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I'm looking for suggestions for a current equivalent (i.e. available!) to the ancient 6551 serial i/o UART... basically, I need a parallel memory mapped interface, baud rates at low speed (don't need more than 9600 or so) and DIP package for preference.

This is to bolt onto the zombie cpu... *I've* got half a dozen 6551s lying around doing nothing, but I think a modern UART would be a better choice.

So far I've found the Intersil 82C50, which is nice as it has the baud rate generator on board, but it's a 40 pin DIP which is a bit excessive in real estate and it's not cheap - pushing fifteen quid.

Or the MAX3100 - but I'd have to bit-bang the interface... and I have no shift instruction (I *knew* I'd find a need for it if I didn't put one in ;) )

Phillips SCC2692 or friends? Hmm, the 2691 has only 24 pins.

Any suggestions?

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Well, a mega8 or similar perhaps.....

sorry, best I could think of now..

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Rob an 8251 or 16450/16550 from an old PC?

Or if want new stuff, SCC2691AC1 from NXP (Farnell 1294824 or 1201303). A new DIP40 16c550 from TI is only €3,32 too.

You could shift to the left by adding the number to itself, then use the MSB :)

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Seems like you'd build one out of ttl chips just for symmetry?

Imagecraft compiler user

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Well i did think of it, Bob, but this is on the IO card, so I figure it doesn't count ;)

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The 16C550 is relatively cheap (2 Euro at my local supplier) and comes also in PLCC package.

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For the "building my own CPU"-fellow freaks: I have one AY-5-1013A UART available: 40pin-DIP UART, all settings in HW, data in and out on two sets of 8 pins. Full datasheet available.

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A GIF is worth a thousend words   She is called Rosa, lives at Mint17.3 https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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@plons
I think I used such an IC for my first cassette-interface.

And here is my entry in the UART-war:
S2350 USART

Correction added later: It was a USRT and no USART
I think....

I used the S2350 to build my first floppy
controller. I think that floppy controller
had more ICs in it than my S4C CPU !

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:)
I used the AY-5-1013A to connect a centronics printer to an Atari800XL, which didn't have a parallel port.
My first floppy-interface was built with an 6820 PIA and an 6850.

The AY-5-1013A may be usefull for David or Neil.

Oh well, maybe it's just a useless antique ;)

Nard

A GIF is worth a thousend words   She is called Rosa, lives at Mint17.3 https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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That's the problem of course. The 6551 would be ideal, but the only supplier is basically eBay... not good if I want to get the project into a magazine. After eating a few of the PDFs I'm starting to be tempted by the MAX3100 - it's got a small footprint even in the DIP package, and of course I can also use it to demonstrate bit-banging the SPI interface.

(And I used the AY chip on an Open University electronics course, sending digital audio down a fibre at around a thousand samples a second :) )

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Neil,
I used in the past code I wrote for a CPLD. It took 12 bits in, serialized it and spit it out. The reciever did the reverse. Works great and ran up to 200mhz. The CPLD's from Atmel are great for this, and the development software is free, and you can get the schematic for a paralel port programmer off the Atmel site. The devices come in a 44 pin plcc package to boot.

Let me know if you would like a copy of the source code I have. It is written in ABEL but can be easily converted to ATMEL's WinCUPL.

Jim

If you want a career with a known path - become an undertaker. Dead people don't sue! - Kartman

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB user

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If you start with the CPLD design, it should be possible to do an all TTL version as well.

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There are 466 pcs g65sc51p1 available in California, fwiw. They are getting scarce, but not totally gone yet 8-)

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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I'd take the old ancient mechanical aproach:

Run it at low speed, attatch the start bit to the first, D0 to the second....D7 to the ninth pin of the relay, stop to the tenth and the eleventh will generate an UART interrupt. At normal (not sending), the relay would be in position 12. Clock generation will be done mechanically. After you do this, you will be praised by many.

http://technology.niagarac.on.ca...

[edit] modified the text a bit to be more suitable for impractical use

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Hey, I used to fix audio routers that worked that way...

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There's this:

http://www.westerndesigncenter.c...

You might have to check if Bill Mesch has it out of sampling.

Jim

Jim Brain

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Quote:
There's this:

http://www.westerndesigncenter.c...

You might have to check if Bill Mesch has it out of sampling.

Jim

Wow! I never knew about this place. I've been manufacturing an industrial temperature controller for the last 20 years that uses the 6502 family. My 6502 inventory is a large "last buy" I made in 1996 8-)

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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I need to keep an eye on that place, just to keep my 6502 hand in...

The zombie io board, though, is now pretty final - I'm just trying to see if everything fits on the board ;)

- 32k 28/6 dip eeprom
- 32k 28/6 dip static ram (small amount gated out for io)
- 82c55 40/6 dip PIO interface
- scc2691 24/3 dip UART
- at90s2313 20/3 dip clock/reset generator
- hin232 14/3 dip ttl/rs232 converter
- OR FT232R SM USB interface
- sundry decoding logic

Proposed pictures later...

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tpappano wrote:
Wow! I never knew about this place. I've been manufacturing an industrial temperature controller for the last 20 years that uses the 6502 family. My 6502 inventory is a large "last buy" I made in 1996 8-)

Tom Pappano
Tulsa, Oklahoma

Yeah, WDC is a very interesting story. Bill was one of the original NMOS 6502 designers, and managed to get Commodore's Jack Tramiel to front money for WDC when he left, promising to cut good deals on CMOS 65XX units. Jack later tried to squeeze WDC out of business, but Bill survived and went on to design the 65C816S, most popular in the Apple II GS.

Jim

Jim Brain

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If you allready have an AT2313 controller on your board, you could use the UART inside that chip. Why do you need an extra UART chip ? It should be possible to get low Baudrates and a resonablely accurate clock from the same crystal.

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I had considered doing it that way - actually, I'd gone as far as to lay out a circuit board - but it has the same issue as the max3100 - communication between the zombie-pc and the serial chip becomes complex.

Anyway, here's today's effort - 32k ram, 8k prom, three bidirectional 8-bit ports (one bit is occupied with a permanent 50Hz timer tick), the UART, USB-serial adaptor, and clock/reset generator all on the one half-eurocard. It was a bit of a squeeze doing it all with DIP...

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Looks very good ! And still some space left....
I expect some gloating coming soon.

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It occurs to me that I could hang an IDE disc drive off that parallel port... :D

Also, swap the ram and rom chips in their sockets and it would work with a generic 6502/6800/6809 processor.

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Nice job Neil!!!

Jim

If you want a career with a known path - become an undertaker. Dead people don't sue! - Kartman

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB user

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barnacle wrote:
That's the problem of course. The 6551 would be ideal, but the only supplier is basically eBay... not good if I want to get the project into a magazine. After eating a few of the PDFs I'm starting to be tempted by the MAX3100 - it's got a small footprint even in the DIP package, and of course I can also use it to demonstrate bit-banging the SPI interface.

I'd seriously consider a M8 or M48 and use it as an uart to the system , ans maybe a few more things. like watchdog or clock gen for the ttl cpu.

/bingo

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Jim 

 

If you still have the source for a usart in a CPLD i like to use it or at least try to fit it in the atmel CPLD that i currently use in a z80 system

 

Bert

Bert Hoogenboom

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That thread is more than 8 years old!

 

West Coast Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net