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Another I2C question

Question asked by cherif.chibane@ll.mit.edu on Oct 16, 2015
Latest reply on Oct 19, 2015 by rejeesh

Hello there,

 

We are moving the FMCOMMS1 to VC707 and we are developing the VHDL to communicate to the FMCOMMS1 via the I2C bus. And I have a questions that I could not clarify by looking through  the previous threads [Yes I did really  look through the previous  posts  :-) ]

 

We would like change the output frequency of the AD4351 within a certain time based on time slot (Ts)

 

- In the FMCOMMS1,  the PIC receives I2C commands form the FPGA and converts them to SPI commands to drive the AD4351.

- To access any register inside the AD4351, we need to do the following:

 

     - Set the transaction ( send I2C commands  to the PIC) and the PIC interprets these commands

     - Do a write command ( send I2C commands  to the PIC) and the PIC interprets these commands

 

Is there a way for me to estimate how long it will take the PIC to receive and translate I2C send them to AD4351.

 

My goal is to have:  T(PIC) + T(AD4351)  < Ts where

T(pic) = time it takes for the PIC to receive and interpret the I2C bits

T(4351) = time it takes for the 4351 to settle to the new frequency.

 

We determined T(4351) by using an AD4351 EVAL board and measured the time it takes for the AD4351 to settle to the new frequency from the time it receives the last SPI   LE   (Latch enable)

 

As usual, thanks a lot

 

Cherif

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