Digital Signal Processing - IP and Algorithms

[simopal6]

Hello,

I need to implement the natural logarithm function and I'm trying to find out if I can use any IP core before implementing it myself. From what I've understood by reading here and there on the web, it could be possible to compute a logarithm by using the Cordic algorithm... However, mathematically, the logarithm depends on the inverse sinh function, which is not implemented by Cordic 4.0. I probably might calculate somehow, but I would need to instantiate too many cores.

Am I making any mistakes or not noticing something or is it actually impossible to computer a logarithm with the Cordic core?

Thank you!

[ywu]

If you use System Generator, you can use the CORDIC LOG reference block in Xilinx Reference Blockset.

[kostbill]

Hello.

I am having the same problem but I cannot use system generator since I don't have MATLAB.

Are there any other ways?

Thank you.

[rcingham]

You could do log2 by a look-up-table, implemented in a psuedo-ROM (by which I mean a BlockRAM initialised to the required value, then never written to).

A bit fiddly, but I have created Pseudo-ROMs for sine and cosine to avoid latency due to CORDIC implementations.

[francism]

Hi Could you could write the log2 function as HDL function and then use that to create your array?

regards

Mike

[juergenatduerr]

the logarithm depends on the inverse sinh function

You can use the atanh instead by expecting ln (x) = atanh((x-1) / (x+1))