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Delay problem while using the pic18f452

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volkvanmyn25

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Hi. I've got a delay problem using the pic18f452. I have been working on a micro brewery controller project using the pic16f877. I upgraded to the pic18f452 because i ran out of program memmory. When i try to compile my code with the new 18f452 i get an "inline delay argument to large " error. I've changed some of the setting to get around the problem. My problem now is, the delay is too fast when i use the pic18f452 but it works with my 16f877. Could it be the capacitor values i've chosen for my 4meg crystal? I've been using 2.2pf caps for many years with a 4meg crystal and pic16f877 and always had success. Sorry, i'm posting from my phone and can't add my code right now.
 

Re: Delay problem with 18f452

in my view 2.2pf is very very small for external capacitor ....if you study the capacitor values in the oscillator section of PIC data sheet they says the value must be 22pf ....
The second thing is if you are using PIC16 to PIC18 family the configuration setting one need to choose properly bcz it is very different for PIC18 series there are think 7 config word registers so you need to put the code to have more clarity ....In my view the code that you are taking is in UART section of inline delay...please correct me if I am wrong...

Good Luck
 

Re: Delay problem with 18f452

I also think the caps might be too small. The drive to the external osc circuit could be different between the two pics. I'll keep you update with my findings. Thanks for the reply
 

Re: Delay problem with 18f452

Its only the caps. look at the data sheet for oscillator config.
 

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