Why does Fixed Point Dedicated Pre Adder with sub direction is not inferred for unsigned multiplier inputs?

Description

This problem can be seen when using Multiply Adder FPGA IP with the following settings:

• Preadder direction set to SUB
• Multiplier inputs set to UNSIGNED  

This is due to multiplier inputs must be signed when the preadder is performing subtraction.

Resolution

To avoid this problem, ensure that multiplier inputs are set to SIGNED when using SUB preadder direction.