Answers Database
COREGEN: How to generate a CORE Generator FIR filter with less than 6 taps
Record #7056
Product Family: Software
Product Line: Coregen
Product Part: Coregen
Problem Title:
COREGEN: How to generate a CORE Generator FIR filter with less than 6 taps
Problem Description:
Urgency:
General Description:
CORE Generator only supports FIR filters with a minimum of 6
taps. How can you generate the equivalent of a FIR filter
with 5 or less taps?
Solution 1:
You can generate a 6-tap FIR filter and set some of the tap
coefficients to 0 to get the equivalent of a FIR filter with fewer
than 6 taps. For example, to get a 6-tap FIR filter which
functions like a 4-tap filter, you could set two of the coefficient
values to 0.
But does this save you any CLBs?
If two of your coefficients are 0, it just means that some locations
in the LUT will be 0. In the PDA FIR filter GUI, you have the
option of enabling the Trim Empty ROMs option to trim out the
CLBs associated with the 0 coefficient taps; however this option
does not exist in the SDA FIR filter, and in the PDA filter, the
output may not be what you expect.
Sample registers are also not optimized away. For a PDA FIR
filter, the sample register consumes n CLBs for the PDA FIR
(where n is the number of bits in the data), and 1 CLB for the
SDA (since data is actually being saved in RAM, not
registers).
Using the 6-tap FIR to implement a filter with fewer taps will not
give you the most optimized solution in terms of CLB utilization,
but may be satisfactory in many cases.
End of Record #7056 - Last Modified: 07/19/99 18:44 |
