Re: How inaccurate is a 555 or 7555 REALLY?

On 8 Dec 2006 14:06:22 -0800, bill.sloman@xxxxxxxx wrote:


John Fields wrote:
On 7 Dec 2006 17:30:41 -0800, bill.sloman@xxxxxxxx wrote:


John Fields wrote:
On 6 Dec 2006 16:18:51 -0800, bill.sloman@xxxxxxxx wrote:


John Fields wrote:
On 5 Dec 2006 21:21:13 -0800, bill.sloman@xxxxxxxx wrote:


Phil Allison wrote:
<bill.sloman@xxxxxxxx>

John Fields:

<snip>

Yes. I've seen them. All very nostalgic. Your recent exercise with a
4024 (the last post in this thread) reminds me of stuff I was doing in
1974 with a 4040, though I didn't decode with three diodes and a
resistor, even back then.

---
Didn't know how? It's just an RDL AND...$

Of course I knew how. But the resistors I would have had to use were
0.6" long and 0.2" wide on the board, so it would have wasted space,

---
Really?

ISTR that 1/8 watt resistors and 1N914s were available back then, so
the entire decoder would have used up the same real estate as an 8
pin DIP, as well as not using nearly the amount of power the TTL
glue you'd have to otherwise make the decoder from would.
---

1N914s weren't a problem, but company policy had fixed on one style of
600mW Philips metal film resistor, and 1/8 watt resistors weren't an
option.

---
Still, you could have mounted it Jap style.

Oh, well...
---


not to mention confusing the final test technicians and the service
engineers.

---
LOL, you design to keep from confusing folks?
---

Of course. Unconfusing them takes time ande costs money. All other
things being more or less equal, I'll go for the transparent design
every time.

---
So you're a proponent of recurrent production costs in lieu of
proper training? How much money do you think you've "saved" over
the years by doing it that way?
---

A more modern programmable logic part - like the Xilinx Coolrunner
series - with in-system programming, 1.8V supply and some really
compact packages - looks as if it would be even nicer, but I've not yet
been able to contrive an excuse to play with one of these parts.

---
You seem to be gravitating toward the "use a PIC" mentality when,
for the OP's purpose, suggesting that he use anything he'd have to
learn to program would be ridiculous. But that's never stopped you
before, huh?
---

A PIC may be programmable, but it isn't programmable logic, and can't
do a lot of things that are easy in programmable logic.

Programming programmable logic can be handled through a variety of
interfaces, depending on the manufacturers programming software
(usually available free for everything except bleeding-edge new parts,
which the Xilinx CoolRunner isn't - Xilinx bought it from Philips).

Most of the ones I've run across have included a graphical option,
which makes the process similar to hooking up logic gates and
bistables.

I prefer to write out a seres of logic equations.

I didn't find any of these approaches difficult to learn - nothing
remotely as difficult as mastering a computer language, where it took
me a week to learn Fortran 4, and nearly a year before I could produce
a well formatted page of output (including printed graphs). The MACRO-8
assembly language for the PDP-8 was much easier - mainly because the
teletype output made more sense.

There is a certain learning curve in learning how to use Boolean logic,
and you need extra time learn how to hook up CMOS parts to realise that
logic - most people would be better off putting the exra time into
learning how to program programmable logic.

The choice of which programmable part should probably be referred to
comp.arch.fpga, but one thing is for sure - you will be able get all
the logic into a single modern PLD.

---
All of which is irrelevant, not to mention boring.

So you don't use programmable logic parts. Why am I not surprised.

---
I don't know, but you seem to be trying to build up this big case
where it's evil _not_ to use PLDs. For me it's not a big deal since
I usually only have a little glue logic surrounding a
microcontroller and the expense and bother of the PLD isn't worth it
when I can use good ol' 74HC and 4000 parts from _anywhere_ to get
the job done. Cheap, too!
---

The glue logic approach was the appropriate way to solve the OP's
problem. End of story.

If you say so John. But you do look a bit silly, bent over, with your
head buried in the sand.

---
Perhaps, but not as silly as you do with yours buried firmly in
Uranus. ;)


--
JF
.

Relevant Pages

  • Re: How inaccurate is a 555 or 7555 REALLY?
    ... John Fields wrote: ... ISTR that 1/8 watt resistors and 1N914s were available back then, ... series - with in-system programming, ... There is a certain learning curve in learning how to use Boolean logic, ...
    (sci.electronics.design)
  • Re: How inaccurate is a 555 or 7555 REALLY?
    ... John Fields wrote: ... ISTR that 1/8 watt resistors and 1N914s were available back then, ... series - with in-system programming, ... There is a certain learning curve in learning how to use Boolean logic, ...
    (sci.electronics.design)
  • Re: How inaccurate is a 555 or 7555 REALLY?
    ... John Fields wrote: ... series - with in-system programming, ... There is a certain learning curve in learning how to use Boolean logic, ... and you need extra time learn how to hook up CMOS parts to realise that ...
    (sci.electronics.design)
  • Re: Impact 8.1 problems with non xilinx device in chain
    ... The PLD pins float during programming. ... You might want to install a strong pull-up on the JTAGSEL to hold it high during configuration and see if that helps things. ... My cursory examination of the Atmel data sheets indicates that the part has 2 pins that control the test modes - a TST and the JTAGSEL. ... JTAGSEL is connected to PLD, everything was fine until I changed the JTAGSEL ...
    (comp.arch.fpga)
  • Re: Xilinx Mode Select Pins
    ... my required programming mode or do I need to connect them to resistors? ... "?During configuration, the Mpin may be tied directly to power or ground, tied High or Low using external resistors, or actively driven by an external component." ... I like to use pull-up/pull-down resistors as it always gives me the option to overdrive the resistor values and change the configuration mode. ... However, depending on the family on the programmed/unprogrammed status of the serial PROM, you can run into some issues. ...
    (comp.arch.fpga)