HS XT LP

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camerart

Well-Known Member
Hi,

When learning to use PICs, I used crystals, thinking this was the way to go. I mainly used 4mHz and set them as XT, thinking that this meant XTAL Crystal. Now I use faster PICs and if I doubt the clock speed, I might experiment with a crystal. Having failed when using XT with a 20mHz crystal and re-reading about it, a penny dropped, that XT doesn't mean crystal, so what do LS XT and HS actually stand for. I think I can guess LS and HS

Hopefully, I will then correct my mistaken interpretation with the correct one.

Camerart.
 
Basically HS is 'high speed', LS 'low speed' and XT 'normal crystal'

Essentially for 4MHz use XT, for 20MHz use HS - between those two take your pick, generally it makes little difference though with 4MHz and 20MHz working fine with either setting. As far as I'm aware the main difference is the amount of 'power' applied to the crystal, as the 20MHz ones are more fragile and 'may' be damaged by the XT setting, likewise the HS setting may not provide enough power to make a 4MHz oscillate. Personally I've never seen a problem either way.
 
According to Microchip

LP = low power, that will give up to 200Khz
XT = medium power, That will give you up to 8Mhz
HS = full power.... The rest!!

If you want low power solutions choose the lowest setting.. If you don't give a monkies about power consumption, then stick it on HS...
 
Hi MM and Nigel,

The way I read and remember things is perhaps more literal than most people, and it does cause me problems. XT is not a clear mnemonic. All three of them can be used for crystals, so why not LS MS and HS, I would get it then.

I only asked the question, as I have had problems in reading these in my unclear fashion for years.

C.
 

Hi Ian,

I understand the concept, but each time I get a problem with timing, as I do now, I don't remember this simple thing. Perhaps I will now after this exchange.

Thanks, C.
 
Simple thing..... If you don't care about power Just always select HS.... OR!!! buy a chip with one in and use INTOSC...
 
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