ID:13497 Verilog HDL error at <location>: exponentiation is not supported for specified operands, <additional details>

CAUSE: Exponentiation support is limited. The limitations are as follows:

Either the exponent or the base must be a constant.
The exponent must be an unsigned number or positive constant.
For non-constant exponents the base must be a power of 2.

ACTION: Change the expression to fit the restrictions. Here is some example syntax:

2**n, where n is an unsigned non-constant
8**n, where n is an unsigned non-constant
var**c, where var is any value and c is constant