Browsing the datasheets, I notice some varieties of PICs have multiple Vss and/or Vdd pins; must they *all* be connected to power, or are they redundant to provide PCB routing flexibility?
I'm referring to straight Vss/Vdd, as opposed to special stuff like Avss/Avdd.
No, I'm not planning to power a whole section of circuits via my micro, but I am wondering what the intent is for those pins.
TIA
Not only should they all be connected, you should add bypass capacitors between all close pairs of Vss Vdd pins. Chips with lots of possible outputs can pull large currents through the Vss and Vdd pins, so having more than 1 pair reduces the IR and inductive drop of the pins and wire bonds. This is especially important if you plan on using any of the chip analog functions without having supply voltage change errors and noise added into their function.
Well, I've just pulled off a Vss on a PIC 16F873 on the protoboard and it carried on working. I wouldn't intentionally leave 'em off though, as they'll be needed to maintain good noise margins under poor working conditions.
I don't know which Pic you're looking at how ever, If it's anything like other chips that do that. If you look at the Vdd description. It maybe labeled as Vdd 2 or something in that order. To give you an example of why this would be.. Lets assume the PIC's internal logic is only 5 volts and you have a bunch of outputs. Now, if you decided to operate these outputs in SOURCE mode, you could then select a different output voltage other than the one the CPU area is using.. for example, the output SOURCE voltage could be 12 volts..
The other options are, internally isolated outputs. this would require a different Vdd and Vss to make it truly isolated output or, if you decide that you don't need the isolation, you then tied them to the same rail.
Also, they some times offer multiple Rail lines for construction and internal power stability..
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
More random STUPIDITY from the Janie TROLL.
Graham
Come back for more "Arm chair bull shit artist" antics
Your comments display lack of colour with your responses which is parallel to your intelligence.
Ever hear the terms?
"You were nothing but a little squirt"
or,
"I scraped you off the sheets" ?
something you might have heard when you were a kid?
So go take a hike pecker head.
-- "I'm never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
At least he's trying to be helpful. OTOH, you're just being a dick........AGAIN!
Now to get nearer to the topic at hand, we're all still waiting to see some modest demonstration of your expert coding ability. I"ve been playing with one of these for a couple of weeks in my spare time, using some icky old C, it's pretty neat IMO:
The problem with Janie is that she gives VERY BAD 'advice'. For her she sees it as a competition to be the stupidest poster in the thread and usually wins the stupidest award by far.
Graham
She? Should I drop my trousers and stick what I have hanging there some where for you? Or should I just wave it around in front of you since you obviously don't have one.
Typical ignorant social disordered psychopath.
P.S. In case you wasn't aware, we're out of the dark ages. It is no longer a standard practice to test voltage with wet fingers. I just thought I would remind you of that because you seem to be a few cells short of a picnic.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
Why discourage him from voltage testing with a wet finger?!
How are your PIC adventures going?
Still trawling through back issues of EPE, that's what I have the most downloaded sample code for. One problem is that the TK3 and SEND programmes have an odd convention with the ORG instruction, using ORG 4 & ORG 5 rather than ORG 0, this could be an unwanted hassle as EPE has standardised on LPT port programmers and my Velleman is RS232 port.
The PIC in Practice book is a bit vague on configuration and header file, I've jumped to chapter 6 which is supposed to explain this as I don't see much point in trying to understand the code examples while I haven't a clue how to set up the configuration that obviously has to come first.
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