EDMA link the paRAM to itself?

Which device are you using?

Which software package and source file does this code snippet come from?

Most likely, the param set is not an active set but is a link set. In this case any time the copy of this link set is exhausted it will be copied again.

Regards,
RandyP

I'm not good at EDMA, but here is some idea to findout the reason why we need to do loop job.

Your code seems to be from OMAPL138/C6748 starterware package and its from McASP example.

It seems, in RX, enable the loop job for all the paramset except paRAM set1.

C:\ti\OMAPL138_StarterWare_1_10_04_01\examples\lcdkOMAPL138\mcasp\mcaspPlayBk.c

/*

** Initializes the DMA parameters.

** The RX basic paRAM set(channel) is 0 and TX basic paRAM set (channel) is 1.

**

** The RX paRAM set 0 will be initialized to receive data in the rx buffer 0.

** The transfer completion interrupt will not be enabled for paRAM set 0;

** paRAM set 0 will be linked to linked paRAM set starting (PAR_RX_START) of RX.

** and further reception only happens via linked paRAM set.

** For example, if the PAR_RX_START value is 40, and the number of paRAMS is 2,

** reception paRAM set linking will be initialized as 0-->40-->41-->40

**

** The TX paRAM sets will be initialized to transmit from the loop buffer.

** The size of the loop buffer can be configured.  

** The transfer completion interrupt will not be enabled for paRAM set 1;

** paRAM set 1 will be linked to linked paRAM set starting (PAR_TX_START) of TX.

** All other paRAM sets will be linked to itself.

** and further transmission only happens via linked paRAM set.

** For example, if the PAR_RX_START value is 42, and the number of paRAMS is 2,

** So transmission paRAM set linking will be initialized as 1-->42-->42, 43->43.

*/

   /* Initialize the 1st paRAM set for transmit */

   memcpy(&paramSet, &txDefaultPar, SIZE_PARAMSET);

   EDMA3SetPaRAM(SOC_EDMA30CC_0_REGS, EDMA3_CHA_MCASP0_TX, &paramSet);

   /* rest of the params, enable loop job */

   for(idx = 0 ; idx < NUM_PAR; idx++)

   {

       ParamTxLoopJobSet(PAR_TX_START + idx);

   }