LogiCORE Multiply Accumulator v4.0 - Why is there no activity on the output of my core during simulation when I set up my Multiply Accumulate v4.0 Core for wide input (e.g., 24x16) and use an output that is less than full precision?

AR#	24096	Search For Another Answer
Topic	IP-DSP Horizontal
Last Updated	09/15/2008
Status	Active

Description

Keywords: MAC, MACC, multiplier, truncate, round, wide

Why is there no activity on the output of my core during simulation when I set up my Multiply Accumulate v4.0 core for wide input (e.g., 24x16) and use an output that is less than full precision?

Solution

In the Multiply Accumulate v4.0 Core, if you select a wide multiply accumulate operation and an output that is not full precision, you will not see any output from the core in simulation.

To work around this issue, you can implement the MACC using the separate Multiply and Accumulate cores available in CORE Generator, Multiplier v9.0, and Accumulator v7.0, respectively. If a rounded output is required, this must be done in HDL outside of the core.