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SRC4392: SRC4392 SRC output sample frequency

Part Number: SRC4392
Other Parts Discussed in Thread: MSP430FR5949


I have posted a question on the output sample frequency of the SRC4392 several months ago and still haven't received any reply.

My question is how you can force the SRC to a specific output sample frequency.

Is the SRC alsways a slave of the output, for instance port-B so you have to program the right sample frequency for port-B and then the SRC will convert any input frequency to the required output sample frequency?

Pls. indicate if this assumption is correct.

Then I have a second question.

I am using the SRC4392 in SPI mode, driven by a MSP430FR5949.

The only way to read data from the SRC4392 at  the MSP430 SPI RX input is to write to the MSP430 SPI transmit buffer.

If I initiate a read cycle to read all of the 51 SRC4393 page0 registers I start by writing the first byte (command byte) 0x81 (MSB one, indicating a read operation and starting at address 1)

The second byte to send is 0x00 (don't care). Consecutive writes to the MSP430 SPI TX register whilst the SRC4392 CD pin remains low will result in SRC4392 data to be sent incrementing the register counter

untill all page0 registers are sent by the SRC4392.  Then I pull the CS pin of the SRC4392 high.

What I want to know is if the CDIN reacts to data at its input during the sending of data to the MSP430, since I have to keep writing data into the MSP430 SPI transmit buffer in order to keep the SRC4392 sending data to the MSP430 SPI RX.

What I anticipate is that once a read command is recognized and the CS pin remains low, the CDIN input is not reacting anymore. Only after the CS pin is cycled (high and low again) the CDPIN looks again at data.

Is this asumption correct.  If not can you explain what the allowed data input is on the CDIN pin during data transmit of the SRC4392, without altering the SRC4293 registers or disturbing the send process to the MSP430 SPI-RX.

Thanks in advance for answering both questions.

  • Hi Jan,
    Apologies for the delay in not getting to your earlier e2e post.

    As far as your first question goes, your interpretation about the basic function of SRC is accurate. The input-to-output sampling ratio is determined automatically by the SRC rate estimation circuitry, with an input and output sampling ratio range of 16:1 to 1:16.

    Regarding the second question, I'll need to look into this a bit more and will have to get back to you w the specifics on the SPI.

    Thanks & best regards,
  • Hi Ravi,

    Any luck yet getting an answer on my SPI read question?