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AR# 40989

Coregen Multiply Accumulator v2.0 - The output is not correct for a 8x8 MACC when either or both input unsigned

Description

Multiply Accumulator v2.0 showing incorrect output. The output is attenuated by a some factor for unsigned input types.

The problem occurs for both software simulation and hardware implementation

Solution

This is the known issue for Multiply Accumulator v2.0 core.This issue applies when either or both inputs are unsigned.

In these cases, the output will be attenuated by a factor of 2 (single input is unsigned) or 4 (both inputs unsigned) and with all the data widths

 

User can workaround this issue by using only signed input type and zero-pad extend unsigned inputs.
e.g. signed_a <= '0' & unsigned_a;


This will result in inputs one bit wider than required, but the hardware used is exactly the same.

 

AR# 40989
Date 12/10/2014
Status Active
Type General Article
IP
  • Multiply Accumulator
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