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MCB2138 processor frequency

I would like to know what frequency the LPC2138 works at after reset. The Xtal is 12 Mhz.

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  • With Startup.s file not open in uVision3, click on Starup.s (in project workspace).

    This will bring up a window showing, Stack Configuration, PLL Setup, etc. Expand PLL Setup. The default shows MSEL at 5 and PSEL at 2. Doing the math with a 12MHz crystal, will give you a frequency of 60 Mhz. The default Pclk divide is 4, (reset value of Pclk divide register) yielding 15 Mhz Pclk.

    Changing these values and recompling should change Startup.s assembly code.

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  • With Startup.s file not open in uVision3, click on Starup.s (in project workspace).

    This will bring up a window showing, Stack Configuration, PLL Setup, etc. Expand PLL Setup. The default shows MSEL at 5 and PSEL at 2. Doing the math with a 12MHz crystal, will give you a frequency of 60 Mhz. The default Pclk divide is 4, (reset value of Pclk divide register) yielding 15 Mhz Pclk.

    Changing these values and recompling should change Startup.s assembly code.

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