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AR# 22598

8.1i Architecture Wizard, XtremeDSP Slice - What bits does the multiplier output when full precision is not used on the output?


Keywords: Xtreme, DSP, slice, MSB, LSB

When generating a multiplier through the XtremeDSP Block Generator, are the LSBs or the MSBs output when full precision is not selected on the output?

For example, if both multiplier inputs are 18 bits and the output is less than 36 bits, will it contain the LSBs or the MSBs?


In ISE 7.1i and ISE 8.1i, the multiplier will output the LSBs.

In ISE 9.1i, this will be updated to use the MSBs for the output that is not full precision.

To work around this issue, output the full precision output and then strip off the unnecessary bits.

For a list of alternative solutions to using the Architecture Wizard, see (Xilinx Answer 30101).

AR# 22598
Date Created 09/04/2007
Last Updated 09/04/2008
Status Archive
Type General Article