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nrf51822 clock interface to mcp25625

hakki goceoglu

Hi All,

I am designing a circuit with nrf51822 and mcp25625 (microchip spi can interface). mcp25625 has an internal 16mHz xtal clock circuit and a digital clock out, I am planning to use this clock out to feed the nrf chip through xc1 input. When mcp25625 is powered on the clock out pin is enabled but the frequency is in 1/8 divide mode, it can later be configured to divide by 1 (16 mHz) output. Would nrf chip start with 2mHz clock? I do not have another cpu, the code to configure the mcp chip has to run on nrf.

Thanks in advance

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    Hi hakki,

    I'll do my best to get you pointed in the right direction on this. First, let me suggest that you read section 13 in the nRF51 (version 3.0) reference manaual. It has a lot of detail on the HF clock operation. I had to read it several times before a lot of it sunk in. I would also suggest that you read section 3.6 on clock management in the nRF51822 (version 3.1) product specification. This will fill in a lot of what you need to know about the clocking system.

    The nRF51822 does have an internal 16MHz RC oscillator that it can start up on. That should be enough to allow you to configure the mcp25625 device to output a 16MHx clock. I would advise that you ensure it can meet the accuracy specifications needed to run the radio if you are planning to do so. I believe it is +/-40ppm.

    There is also some very good information about clocking in the answer to this question: clocking answer

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  • 0

    Hi hakki,

    I'll do my best to get you pointed in the right direction on this. First, let me suggest that you read section 13 in the nRF51 (version 3.0) reference manaual. It has a lot of detail on the HF clock operation. I had to read it several times before a lot of it sunk in. I would also suggest that you read section 3.6 on clock management in the nRF51822 (version 3.1) product specification. This will fill in a lot of what you need to know about the clocking system.

    The nRF51822 does have an internal 16MHz RC oscillator that it can start up on. That should be enough to allow you to configure the mcp25625 device to output a 16MHx clock. I would advise that you ensure it can meet the accuracy specifications needed to run the radio if you are planning to do so. I believe it is +/-40ppm.

    There is also some very good information about clocking in the answer to this question: clocking answer

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