Availability of 8751

I think, 8255 could be a bigger problem...

best regards

Stefan DF9BI

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-- StoneThrower

You can probably buy some quantity of "pulls" or new-old stock. They have not been made for more than a decade, so expect the price may be relatively high and the condition to perhaps be dubious.

It greatly depends on the details, but something that old would likely benefit from a complete redesign if it's a profitable product, and the one "I" would use would be heavily dependent on the details of the application. Atmel 8051 processors are fairly close if firmware reuse was important.

Do you have the code for the 8751H ?

If you intend to re-write the code, you can stay with the 51 family or you can use most any chip in a 40-pin DIP package ( with minor re-wiring).

If it is a new design, new PCB and new packaging, how soon do you want this done ?

So it depends.

don

You might want to consider using an FPGA to replace some or all of the parts. There are several vendors that sell 82XX and 8051 type of cores. If you can't change the PCB then companies like Enterpoint in the UK sells some very nice DIL FPGA based replacement boards

Hans

We're still buying 8255A's in PLCC through distribution.

repalcements?

re-wiring).

Well, I can't give out too much info (my employer wouldn't like that). I have the code. The machines are used to process info, but are not mass produced and are not sold to other companies. Our 'product' is processed info.

It's a real time embedded system using feedback sensors that create interrupt signals for the controller boards.

My goal (as is the goal for many engineers) is to make the machines fast, reliable and maintainable.

Most of the 74 series TTL boards have been replaced with FPGAs, but the int. driven MCU and parallel bus cont. has not changed.

The way I want to do the redesign is to put everything onto FPGAs. I've synthed a MIPS processor for a class in school, but used very few instructions, and no interrupts.

How complicated is it to synth processors with interrupts?

Are interrupts more efficient than just using state machines and combinational logic?

I would like to use VHDL code from someone else that has already looked at these chips for that, but I don't want any legal issues or pay royalties.

I like to use VHDL, but my co-worker likes to use .bdf files directly into Quartus.

I'm sure a modern (curently available) 8 bit MCU with 4K ROM can handle it, but there are too many to choose from. I guess any would do. I think most people stick to what they are familiar with. I've programmed

There are 8052 cores available free and for cash. Plus several companies make chip While it is old, it is still an active family of parts. Just not from Intel

Since this is a stable function, low volume product, then "if it ain't broke, why fix it ?"

Look at

a) DIP 5V '8751' replacements are very widespread. ( I guess this does not use external CODE memory ?)

b) Plenty of 8255s appear, fine for product maintenance. (jameco show 3 versions)

c) As for b) jameco show two variants.

If you DO want to do new designs, and expand the code, then stick with the code base you have, and also the other framework you have. (ie 5V)

So, for a good 5V controller, with more than 8255/8254 inbuilt, look at the new SiLabs C8051F58x / 59x/

- On chip debug, ADC. lots of timers, and 64K FLASH, direct 5V operation, Ex Stock...

-jg

repalcements?

Thanks for the feedback. I'll look at the Atmel and SiLabs options.

If I told my boss: "if it ain't broke, why fix it?" I'd be gone in a week. ;)

We still use HP1000 mini's in our system that are 20 years old, but 'ain't broke'. Would you keep using them also?

Why ? A smart boss will have you working on the things that need fixing first. Simple priorities....

If they did the job, sure.

But it is also smart to ensure you have a transition plan, and know that should one fail, you can swap-in a newer replacement as needed.

-jg

... snip ...

More like 30 years old. Perfectly usable. So the answer is 'yes'.

use?

with

Because 'reactionary engineering' is a good way to loose a job. Saying something like that would imply that I don't care. Besides, that wouldn't be much fun.

'ain'=

That's why they're still here so far, but the day comes in every computer's life. Sure, I could still play 'Pong' all day, but wouldn't you rather play Call to Duty 4?

BINGO!