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'[EE]:Observations and questions'
2001\01\01@003232 by Justin Richards

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Hi and to all a happy new year,

New to pics!

1. I have a 16F84 config  in HS with 3.2768 Mhz Xtal and 2x20pf caps to GND.  I was expecting a reasonably accurate time base but after an 8 hour test was about 8 secs slow.  I have seen in other MSG's reference to 32 khz watch xtals used but thought that the error would have to be less using a Mhz xtal

Should I get better accuracy than this and if not how is a more accurate timebase derived.

I get my *second* from the following

fsec = 3 276 800 / (execution rate * prescaler * max count tmr0 * FILE counter)
       =3 276 800 / (4 * 128 * 256 * 25)
       =1


2. Used CMOS chips(4094) for the first time (always used TTL cause I like em) on this project and powered up before checking connections (as I tend to do) all worked well.  Then discovered that the GND pin was not connected.  Was impressed to see this chip function as it was sinking current for a seven seg disp. Just an observation

3. What does TTYL, IMHO, FAIK, AFAIK (and any others I may run into) stand for.

4. Windose (hee hee) ME does not appear to have the 'attrib' command and cant believe they took away DOS MODE. (Still has a DOS Box thou )

5. What does it mean to have an embedded processor?. Is the processor in my washing machine embedded? Is the HC11 an embedded processor? Is the one in my PC embedded?
Regards
Justin

ps Thanks for some really interesting reading even managed to answer some but by the time I get to reconnect I find the topic completely thrashed out.  I must confess since subscribing I have spent very little time actually doing the project and wonder just how some of you find the time to do both.  Thanks again


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2001\01\01@010619 by Bob Blick

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>1. I have a 16F84 config  in HS with 3.2768 Mhz Xtal and 2x20pf caps to
GND.  I was expecting a reasonably accurate time base but after an 8 hour
test was about 8 secs slow.  I have seen in other MSG's reference to 32 khz
watch xtals used but thought that the error would have to be less using a
Mhz xtal

Didn't look at your code, but there could be two hardware reasons. HS mode
at 3 MHz is driving your crystal pretty hard. Or maybe you are using a
series crystal, you should use a parallel crystal.

Cheers,

Bob

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2001\01\01@074711 by Anand Dhuru

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Is the lag always about 1 sec / hour? in which case could it be the software
overhead not taken into consideration?

Regards,

Anand
{Original Message removed}

2001\01\01@085636 by mike

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On Mon, 1 Jan 2001 13:27:58 +1100, you wrote:

>Hi and to all a happy new year,
>
>New to pics!
>
>1. I have a 16F84 config  in HS with 3.2768 Mhz Xtal and 2x20pf caps to GND.  I was expecting a reasonably accurate time base but after an 8 hour test was about 8 secs slow.  I have seen in other MSG's reference to 32 khz watch xtals used but thought that the error would have to be less using a Mhz xtal
>
>Should I get better accuracy than this and if not how is a more accurate timebase derived.
You can normally expect 50-100ppm from a normal crystal (excluding
temp changes) so something is wrong - using HS mode is probably not a
good idea as it will be overdriving the xtal.

>2. Used CMOS chips(4094) for the first time (always used TTL cause I like em) on this project and powered up before checking connections (as I tend to do) all worked well.  Then discovered that the GND pin was not connected.  Was impressed to see this chip function as it was sinking current for a seven seg disp. Just an observation
CMOS chips (ebven PICs) will often 'find' power and GND via their
input protection diodes if unconnected. Needless to say you are also
likely to see some strange things happening....
>3. What does TTYL, IMHO, FAIK, AFAIK (and any others I may run into) stand for.
Talk To You Later, In My Humble Opinion, For All I Know, As Far As I
Know

>5. What does it mean to have an embedded processor?. Is the processor in my washing machine embedded? Is the HC11 an embedded processor? Is the one in my PC embedded? Generally, a processor is described as 'embedded' when the presence of
a processor is not directly obious to the user, and/or 'data
processing' is not the principal purpose of the product. Any processor
_can_ be (and probably has been) embedded, but small microcontrollers
like the PIC are by far the most common, being specifically designed
for this type of application.

Obviously there is some scope for semantic arguments, but the main
processor in your PC would not normally be described as being an
embedded processor, but the ones in your keyboard, mouse, printer,
modem etc. would.
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2001\01\01@094452 by Olin Lathrop

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>>
1. I have a 16F84 config  in HS with 3.2768 Mhz Xtal and 2x20pf caps to GND.
I was expecting a reasonably accurate time base but after an 8 hour test was
about 8 secs slow.
<<

That's .03% accuracy.  What's the crystal rated at?  Also, are you sure you
need HS mode?  I don't have the 16F84 data sheet in front of me, but usually
you don't need HS mode until 4 or 8 MHz.

>>
3. What does TTYL, IMHO, FAIK, AFAIK (and any others I may run into) stand
for.
<<

It stands for "I'm too lazy to type a few extra letters and too arrogant to
care that not everyone can remember all the silly abbreviations".  I usually
just skip over this crap when reading, especially if the poster wants
something from me rather than the other way around.  I sorta recall IMHO =
In My Humble Opinion, AFAIK = As Far As I Know, and I don't remember TTYL.

> 5. What does it mean to have an embedded processor?.

An embedded processor is one that is built into something for performing a
particular dedicated task.  The end user doesn't have access to the
processor to run arbitrary programs.

> Is the processor in my washing machine embedded?

Yes.

> Is the HC11 an embedded processor?

Embedded is defined by use, not by processor type.  However, those
processors like the HC11 and PICs that are designed for embedded
microcontroller use usually don't have the facilities to make them viable
non-embedded computers.

Some of the processors that are designed for general purpose non-embedded
computing can also be used in an embedded way.  One project I worked on used
a Pentium as an embedded processor.  This same machine could have run
Windows, but instead was running a real time control program.  Various
flavors of the Power PC are often used in embedded systems that need
significant horsepower.

> Is the one in my PC embedded?

No.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, .....olinKILLspamspam.....embedinc.com, http://www.embedinc.com

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2001\01\01@180656 by Bill Westfield

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>
       3. What does TTYL, IMHO, FAIK, AFAIK (and any others I may run into)
           stand for.

   It stands for "I'm too lazy to type a few extra letters and too
   arrogant to care that not everyone can remember all the silly
   abbreviations".

Hmm.  Must be Olin... :-)

In addition, these are largely "noise phrases" that add little meaning
to the actual message, but would be present in conversation.  They're
"verbal cues for a non-verbal medium."  TTYL == Talk To You Later,
IMHO == In My Humble Opinion, IMO == In My Opinion, IMNSHO == In My
Not So Humble Opinion (sometimes I actually take care to notice the
difference between these.  There can be quite a different meaning...)
IIRC == If I Recall Correctly, RTFM == Read The Manual, AFIAK == As
Far As I Know.


   I usually just skip over this crap when reading, especially if the
   poster wants something from me rather than the other way around.

And you usually won't lose much meaning by skipping over them...  The
presence of many such abbreviation certainly means that the discussion
is "conversational", rather than presentational or formal, I think.
Messages containing technical info along with conversational idioms
would be somewhat less trusted than a more formal written style.


   > 5. What does it mean to have an embedded processor?.

   An embedded processor is one that is built into something for performing a
   particular dedicated task.  The end user doesn't have access to the
   processor to run arbitrary programs.

   > Is the processor in my washing machine embedded?

   Yes.

   > Is the one in my PC embedded?

   No.

However, your entire PC could be "embedded" in some other application (say,
a console monitor for a collection of network servers), at which point it
(the whole computer) WOULD become an embedded system - there are certainly
"embedded operating systems" aimed specifically at PC compatible hardware.


BillW

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2001\01\01@182947 by Mike

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Justin Richards wrote:
<snip>
> > 3. What does TTYL, IMHO, FAIK, AFAIK (and any others I may run into) stand for.

Try this link for a rather lengthy list of Internet acronyms.
http://www.netlingo.com/emailsh.cfm
-- Mike Werner  KA8YSD   | He that is slow to believe anything and
                     | everything is of great understanding,
'91 GS500E            | for belief in one false principle is the
Morgantown WV         | beginning of all unwisdom.



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2001\01\01@203423 by Gordon Varney

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>
>         3. What does TTYL, IMHO, FAIK, AFAIK (and any others I may run
into)
>             stand for.
>
>     It stands for "I'm too lazy to type a few extra letters and too
>     arrogant to care that not everyone can remember all the silly
>     abbreviations".

Personally, I find the abuse of acronyms in the Engineering field to be
horrific.
That's why I joined the AAAAA (American Association Against Acronym Abuse)

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