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What does the XTAL directive really mean?

I am confused by the documentation. It states in the "Getting Started" book that the XTAL [directive in the Target dialog] specifies the CPU clock for my device. "In most cases this value is inentical with the XTAL frequency." When is it not? And if not what do I enter into the field? I am using the EZUSB part from Cypress. I believe that the actual CPU clock speed for a 12MHz crystal would be 48MHz. Should I enter 12 or 48?

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  • "The Keil simulator uses the XTAL frequency to establish timing values like how many real-time seconds it takes to execute instructions and serial port baud rate calculations."

    As we guessed - but why doesn't the manual clearly tell us that?!

    The point of having a manual is so that we can read it and know how to use the product - not try to guess what needs to be entered for a particular setting!!

    We still don't know when we should enter the crystal frequency, and when we should enter something else; nor how to determine the "something else" value in those "unusual" cases!

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  • "The Keil simulator uses the XTAL frequency to establish timing values like how many real-time seconds it takes to execute instructions and serial port baud rate calculations."

    As we guessed - but why doesn't the manual clearly tell us that?!

    The point of having a manual is so that we can read it and know how to use the product - not try to guess what needs to be entered for a particular setting!!

    We still don't know when we should enter the crystal frequency, and when we should enter something else; nor how to determine the "something else" value in those "unusual" cases!

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