With an accuracy of..??Originally Posted by mackrackit
Better or worse than a good crystal? (10-20ppm?)
Just curious, but too tired to go hunt up the 1337 data sheet...
steve
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With an accuracy of..??
Better or worse than a good crystal? (10-20ppm?)
Just curious, but too tired to go hunt up the 1337 data sheet...
steve
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I guess it is about the same as a good crystal.
DS1337C ONLY
The DS1337C integrates a standard 32,768Hz crystal in the package. Typical accuracy at nominal VCC and +25°C is approximately +10ppm. Refer to Application Note 58 for information about crystal accuracy vs. temperature.
Dave
Always wear safety glasses while programming.
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Well, without reading AN58, it sounds comparable to a decent crystal.
Or is it..?at nominal VCC and +25°C
Sigh... so many data sheets, so little time...
steve
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Ok, I don't know why I thought it was the chip datasheet that claimed a certain degree of accuracy.
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If you want precise time keeping, an idea would be to use a cheap GPS module with PPS signal output (1 pulse per second).
Ioannis
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I use on average a couple of thousand DS1307's annually. If it's better than 15 minutes per year (and that's matching it exactly with a 12.5pF xtal), you've got a good one. For the money you pay (say around $0.75 in quantity) they are totally rubbish.
I keep meaning to program up a 18F part with a secondary 32kHz xtal and have a background interrupt timekeeping program... finally consign the 1307 to anals (deliberate spelling) of History.
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That is interesting. I only use around ten per year so I do not have the kind of data you do, but I typically see errors less than a minute per six months.
Maybe the built in crystal in the DS1337C is better???
Dave
Always wear safety glasses while programming.
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