Painless micro program

PLC ????

Just to open the box of a PLC will cost over $200.

Let alone getting the rest of the project done.

What PLC are you talking about ??

donald

How many of you have tried working with a Fairchild 3850 (F8)? The program counter(s) was not on the cpu chip.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller

Hey, i liked 1802s beter than 8051s or 6502s and about as well as 6802s.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller

Some of IBMs early micros had a shift register instead of a program counter. The PPC-970 (and Power4/5) have no program counter at all. ;-)

--
  Keith

There are some people that like hitting themselves on the head with a hammer too.

8051s are *the* best micro on the market today. :)

Just found this.

Now here is a guy with too much time on his hands :-)

6802 wasn't bad, except that not being able to push the index register made it tricky to write an RTOS.

John

Some of National's early COPS machines used a pseudo-random shift register as the PC. So sequential instructions were scattered all over memory. I am *not* kidding about this.

John

Ick! Having a stack (not all processors have one) and not being able to push some resources to it is really ugly! How do they suggest that this be handled? What was the rationale/excuse for not being able to push an index?

--
  Keith

As I mentioned above, IBM did the same thing. LFSRs are cheaper than counters. It mattered once.

Though the first national microprocessor I used was the PACE. It was quite a nice processor and 16-bits in the mid '70s (though the ALU was only 8 bits).

--
  Keith

Actually, the 8051 is quite repulsive, at least as far as the on-board timer goes. I made an interface once from ASCII to RC PWM, and it wasn't as much fun as, say, a 68HC11 would have been.

I've never used an 1802, but from the data sheet it looks like it's not very friendly.

But I've used a 6502 to make a keyboard scanner with N-key rollover - I found its architecture very pleasant to work with, except for the 256-byte limit on the stack, but how deep do you need to call when all you're doing is scanning a keyboard? :-)

Sorry for contributing to the religious uP wars. ;-)

Cheers! Rich

Because it feels good when you stop? ;-)

Cheers! Rich

with no specs I'm talking in general.

the guy wants "painless to program" and doesn't mention a budget, or familiarity with any programming language.

AIUI PLCs are fairly easy for those with no software experience to program.

Bye. Jasen

On May 19, 12:43 pm, Rich Grise wrote: [....]

What problem did you have with the timer? It seems to work quite well for me. Perhaps you didn't get it set up correctly. There are quite a few options on how to use it.

[....]

It is a good example of how not to make a micro. It acts a great deal like the registers were one chip and the ALU part was another and they just grafted them together.

It was extremely slow because each instruction took 12 clocks and didn't do much. There are a few nice things about it. The fact that it was one of the few processors with DMA built in was one. It was also very low powered. It was CMOS at a time when others were NMOS.

I'm with you. FOr a processor with an overly complicated memory architecture and horrible ISA, it's a nice processor for many embedded projects. The selection of peripherals makes it very nice.

Well, the 8051, at least in its original incantation, isn't much of a screamer either (12 clocks per op, as well).

Not very. Almost every computer keyboard on the planet has an "8048" in it.

No you're not. ;-)

--
  Keith

There's a big difference between 12 cycles of a 12MHz clock and 12 cycles of a 2 MHZ clock. Besides:

A = B + C

Compiles to something like 16 instructions if A, B and C are randomly located in the RAM area.

[....]

I think today it is more of a 8048 like core in a special chip. I wouldn't be surprised to see only one package inside a keyboard. With the kind of quantity they are made in today a special purpose IC makes a lot of sense.

Please send link about programming PLCs.

What I have seen, PLCs are like programming in Forth, a write only language.

You don't debug, you re-write.

donald

There's nothing wrong with ladder logic. Although I've not programmed exensively in it, I've designed products that accept forms of it. People who are drawn to graphic representations rather than procedural languages might even prefer it, despite the electromechanical paradigm. Having a 'hardened' hardware platform is certainly worth something in many situations too.

Best regards, Spehro Pefhany

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Like I said, there isn't much of a difference.

The 8051 is not so different if A, B, and C are randomly located in external RAM. I'd never use a HLL on such a beast.

Which is why I put 8048 in quotes. My bet is that the 8048 core is still in there.

--
  Keith