Hello, I am implementating Fixed point signed multiplication. Is there a algorithm to implement it. I have done the usual method of multiplication i.e partial products ...shift and add method. But its very slow. If you know any algorithm which will faster do mention. Any reference will be great. How does the signed multipliers in xilinx that fast. what algorithm do they use. I need to first implement in on MATLAB and see the result.
waiting for reply praveen
Do you need the full (double-wide) result, or just the lower N bits of an NxN bit imul?
The fastest pure sw method I know (for relatively small values of N) is to use branchless conversion to absolute values, do the multiplication via a lookup table of squares, and then a branchless fixup of the sign at the end.
Terje
-- - "almost all programming can be viewed as an exercise in caching"
In VHDL, use a signed type and use '*' - synthesis should generate a good result.
In current verilog, just use a signed type.
In older verilog versions you can simply sign extend the inputs to the width of the result and perform an unsigned multiply. Synplify will recognize this as a signed multiply and trim the input arguments back down.
Synthesis tools should give you a good implementation directly. All you need to do is figure out where the binary point went and take the bits you want.
praveen wrote:
Praveen,
have a look at the multipliers page > Hello,
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