6670 AIF2 CPRI Generic Packet Test Framesync timing

Hi Sahil,

I have been able to understand that part also by following the configuration just before your reply. I have another question though, could you guide on the utilization of the frame period, in other words in how much of the frame period can data be transmitted? Since the example runs FDD I am guessing transmit is possible after the delta offset of the frame but I need to be sure for proper communication between devices.

Also I have one last question, how many milliseconds do 2457599 tx byte clocks correspond to? I have measured the time interval and my measurement was 7.8 milliseconds which did not make sense to me (I was expecting 5 or 10 ms).

Best Regards,

ilke

Hi Ilke,

Thanks for your patience on this one. When we are running FDD the AIF2 links can utilize the entire bandwidth of the air channel. Data can be transmitted after the delta offset, you are correct.

For your second question, 2457588 tx byte clocks is the radio frame size for CPRI and does in fact correspond to 10 ms. For CPRI one dual byte clock is 245.76 MHz in duration, so we can calculate the frame size as below:

radio frame duration = # of dual byte clocks in frame * duration of dual byte clock

2456599 dual byte clocks * ( 1 sec/(245760000 dual byte clocks) ) = 0.00999...  which gives you ~10 ms.

Please let me know if anything is unclear.

Regards,

Sahil

Hi Sahil,

I have been doing measurements with the timer of the 6670 DSP and am still getting results around 7.8 ms. When I change the timer period to symbol from frame then it becomes 0.78 ms. The configuration is as it is in the source code that is provided by TI.

   //AT Event setup (Event 7)
   AtEventSetup.AtRadEvent[7].EventSelect = CSL_AIF2_EVENT_7;//Select Event 7 
   AtEventSetup.AtRadEvent[7].EventOffset = 400;
   AtEventSetup.AtRadEvent[7].EvtStrobeSel = CSL_AIF2_RADT_FRAME;
   AtEventSetup.AtRadEvent[7].EventModulo = 2457599;
   AtEventSetup.AtRadEvent[7].EventMaskLsb = 0xFFFFFFFF; 
   AtEventSetup.AtRadEvent[7].EventMaskMsb = 0xFFFFFFFF; 
   AtEventSetup.bEnableRadEvent[7] = TRUE;//Enable Event 7

As I have read from the user guide this can not have anything to do with DSP core frequency (which is 1.00 GHz) since it uses an external clock as input to its timers. 

I have tried modifying the EventModulo to see if anything changes but since the timer is related to the radio protocol that is selected that did not work out either. 

Now either my timer is not functioning which has a frequency of 166.7 MHz (1.00 GHz / 6 which is specified in the data sheet) or there is another problem that I can not understand. 

My timer counts 1310000 for one frame period, which is 1310000 * 6 ns ~= 7.8 ms.

I hope I am clear enough. Thanks for your continuous and tireless help.

Best Regards,

ilke  

Hi,

I was reading the Q and A and it was really helpful in understanding some concepts related to the AIF2 in generic packet mode. However, a few questions I would like to ask from all on this forum.

A CPRI basic frame consists of AxC slot and CW slot. Can we use both (AxC and CW) to transfer user data when CPRI is used in generic packet transfer mode? If yes, what would be the register configuration for the Protocol Decoder? If only AxC Slot is used to transfer the packet, what configuration or settings is required for the protocol decoder?

Thanks,