piclist 2001\01\01\085636a >
Thread: Observations and questions
www.piclist.com/techref/index.htm?key=observations+questions
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face BY : mike@spam@@.....whitewing.co.uk



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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In reply to: <02f601c0739a$960a7740$cc6528cb@jkrichards>
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