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Original question:

Does LM3279 supports rffe extended read/write commands?

LM3279 - RFFE Interface Related Questions

Mano Prabha Ganesan26
Prodigy 60 points
Other Parts Discussed in Thread: LM3279

Hi,

I have the following questions with LM3279,

1. I understood like the Slave Address is programmable through RFFE interface. But I was not able to successfully change the slave address. I tried writing the value 0x16 to the register addr 0x1F. But the new value is not reflected. It will be helpful if I can get suggestions to programmatically update slave address (USID)

2. Also, is there any option to increase the driver strength of the RFFE interface lines?

3. With respect to the device response rate, will the read back is always at half speed when the operating frequency is greater than 13MHz? Or, is the slave capable of responding back at 26MHz rate?

Please help with the inputs for the above items.

Thanks,
Mano Prabha

  • 0
    TI__Expert 6330 points
    Hi Mano,

    Allow me to look into this. Please expect a response by 1/23/18.

    Thanks,
    Aaron
  • 0
    TI__Expert 6330 points
    Hi Mano,

    1. You are correct that the USID should be able to be set via this register. I am having the same issue as you when setting this up on the bench though. This is the only way that I see documented to update the slave address.

    2. You should be able to use a buffer to increase the drive strength.

    3. We do not have a setup to operate at these speeds on the bench. When the RFEE is operating in the kHz range, it does appear the LM3279 responds at a slower rate than the master. This would suggest your statement is true.

    Thanks,
    Aaron
  • 0 in reply to Aaron Goodson
    Prodigy 60 points

    Hi Aaron,

    Thanks for your inputs.

    On #1, I understand that you are also observing an issue in changing slave address. Can you please help getting the procedure to change the slave address if it is possible? If not, could you confirm if this is an issue? Because the device behavior and the data sheet descriptions on Device Enumeration are conflicting. Correct me if I am missing something here.

    On #3, Based on your observation, we are concluding that the device will always respond at half speed. So, the maximum device response rate is 13MHz. Correct me if this is wrong.

    Thanks,

    Mano Prabha

  • 0 in reply to Mano Prabha Ganesan26
    TI__Expert 6330 points

    Mano,

    1. After looking further into it, the RFFE standard has some nuance to it in order to change the USID. The product and manufacturing IDs of the device need to be written to the product and manufacturing Id registers. Even though these are read only registers, the values that are in the register need to be repeated to these registers to allow altering of the USID. Refer to the image below for more information. This procedure will also need to be done every time the device is power cycled. 

    3. I'm not sure it will always be at half speed, but it does appear to respond at a slower rate. For the setup we currently have, the master writes at ~400kHz and the slave responds at ~300kHz.

    Thanks,

    Aaron

  • 0 in reply to Aaron Goodson
    Prodigy 60 points

    Thanks Aaron, this information is helpful!