Selecting TDM8 streams into DSP

I think I have answered my own question.

It seems the Automatic Input Channel Assignment routes data from the Serial Inputs sequentially as required so in my proposal above I would get the 24 signals from the first 3 TDM8 streams into the DSP core, I only want to access 1 or 2 channels at a time.

The only thing I can think of would be to program the lower number Serial Inputs back to TDM2 which would 'rob' two channels from the core but would then drop higher TDM8 streams into a 'visible' position.

Eventually if I programmed all the lower Serial Inputs (0 to 6) as TDM2 I would have lost 14 channels input to the core but I would be able to access the last 8 channels on SDATA_IN7 as channels 15 - 22 in the DSP core.

Could anybody confirm this is how it works?

Or is there any simpler way to get this kind of access? I have looked at the "Serial Input Flex modes" but I don't really understand what they do.

PhilipJ

Hello Phillip,

Changing the lower inputs to either TDM2 or to "No Data" would indeed rob two of the core's channels. But, you are correct in that you can expose channels that were excluded because you had "used up" all 24 inputs with previous inputs.

I don't think that flexible TDM will help you in this situation. It is designed to pack and unpack unconventional serial data formats. It is a bit confusing to use. It works on a byte by byte basis.

You could go to two parts. Two ADAU1452's would allow you to actually process all 64 channels at a time. But, I understand the cost and space issues.

Dave T

Hi Dave,

thanks for the comments.

We have decided to use a small FPGA externally to route up to 3 of the 8 TDM8 streams in for processing.

regards

Philip