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Can we use SPI interface to act as a clock source ?

chandra mouli
Prodigy 110 points
Other Parts Discussed in Thread: MSP430G2213

Dear All,

Iam planning to use MSP430G2213 for my project.

I have an ADC also.

Is it possible to use the CLK out of the SPI interface available on the microcontroller to

provide clock to the ADC?

Is there anyone who had done that ?

The clk source is typically 15-20MHz

My objective is to reduce the total number of IC and also the cost.I don't want to put another clock generator for the ADC.

Or can anyone suggest a clock generator source of 20-25MHz with a cost cap of 0.5$ ?

 

Thanks a lot

chandramouli

 

  • 0
    Expert 1170 points

    Well, based on the datasheet the max frequence for the USCI (that contains the SPI module) is 16MHz... A problem could be that  you cannot generate a continuos clock signal with the SPI module (you have to continously restart SPI communication).

    A simpler way could be to use the SMCLK output. The MSP430 has three internal clock signals (ACLK, MCLK, and SMCLK). There is one setting of the DCO that generates a frequency of min 16MHz and max 26 MHz - so the chip to chip variation may be quite different! So if this frequency is selected you can use the DIVMx divider within the clock system to adjust the MCLK within its allowed frequency range. And SMCLK could run at 16-26MHz. However, this means that SMCLK cannot be used on the chip anymore; this means all periperals that usually would use SMCLK as its high frequency source could not be used.

    If 15MHz are good enough for the ADC I would adjust 15MHz for DCO frequency and use it for the SMCLK as source. In this case the SMCLK would be available for the peripheral modules. You just have to ensure that the minimum supply voltage for this frequency is applied!

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