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The relation between crystal and the speed of mcu?

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pic16f84

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diffrence between

i want understanding information about realation between crstal in microcontroller and the microprocesser speed i hope for any one have information to give me
thnk you
 

diffrence between

Well,
your name pic16f84 makes me wonder which architecture you might be talking about ;-) The PIC architectures are a little bit sluggish, they need 4 oscillator clocks to execute the simplest instructions. This means that a PIC running at 40 MHz is as fast as an AVR running at 10 MHz.
You need to ask for specific architectures to compare them. This information is not always easy to find, in particular if it is to the disadvantage of the architecture. 40 MHz seems so much faster than 10 MHz on a competition device but surprise, it is not!

This should get you started, Bob
 

Re: diffrence between

For most of the popular microcontrollers they need four osc clock cycles to complete one device cycle. Different instructions need different number of cycles. For example, a shift instruction need one device cycle that is four osc cycles, and a branching instruction may need two device cycles that is eight osc cycles. Some advanced MCUs need less osc cycles to complete one device cycle.
 

Re: diffrence between

In the PIC, yes there are four clock cycles for each instruction, but that does not mean the pic is sluggish, compared to ANY other processor. Anyone who tries to tell you that is trying to make up for his own inadequacies. Each processor has its strengths and weeknesses, and all are quite good. On each clock cycle (fO/4) an instruction is executed, unless there is a call which requires a jump, in which case the instruction must be flushed from the pipeline. The instruction then takes two cycles to execute.
It may also help you to know that with increased clock speed comes increased complexity in routing your circuit. High frequency circuits often have more problems with noise, than low frequency.
Regards,
Robert
 

Re: diffrence between

in pic the Fosc is divide by 4 so a 20 Mhz crystal will generate 5 MIPS .
 

Re: diffrence between

Read the 'Mid range Reference manual' from microchip, it's undoubttly writted on
 

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