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Coefficients in 21469 FIR Accelerator

Question asked by maboytim on Feb 28, 2010
Latest reply on Mar 15, 2010 by Mitesh

In the FIR TCB there is a coefficient count/length, a modifier, and an index - but no base.  How exactly do these work?  Since there is no base I assumed the index served also as the base - that is, your coefficeints have to start at the base - and it would follow the usual circular addressing.


I want to implement a polyphase filter with one coefficient set for even numbered outputs and another set for odd numbered outputs (that is, two phases).  I created a coefficient vector with two coefficient sets (one right after the other) and made my coefficient count/length twice the TAPLEN in FIRCTL2, but it doesn't seem to be using the second set of coefficients, only the first.  For example, if one of my coefficient sets is all zeros then either all of my even or all of my odd samples should be zero, but if I make the first set zero then all the outputs are zero and if I make the second set zero then no outputs are zero.


I thought I read somewhere in the documentation some comment regarding circular addressing for the coefficients but I can't seem to find it again.


Can anyone clarify how the coefficients are accessed?