changes in the constant parameter affecting the logic

A constant is meant to be there as constant for some purpose.

You tell us why do you want to change it and what does it do?

A constant is not variable(I believe) and is used instead of embedding numbers directly in code in various parts that makes it difficult to change for any future update or purpose.

Changing value of x changes the logic means obviously x is being used in the logic to affect the result. So obviously you cannot randomly change value of x without first understand what it does. You need to see where x to used and how it's used and then things will become clear.

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Making some unwanted changes which is not a logical change affecting the complete logic...

For eg.. VHDL syntax

constant x : std_logic_vector(15 downto 0):=x"af11";

this value is used in my logic while transmitting a ethernet packet. if i am changing the constant parameter to any other value my logic is not working.

what could be the issue?

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