Performs an Integer Subtraction with Borrow between both 8-bit wide input values. The following listing shows the VDHL description of the SBB operation. To perform the SBB operation with the Ripple Carry Adder, the Carry-Flag from the previous SUB operation is added to the 2nd input parameter. And finally the Ripple Carry Adder performs a Subtraction by converting the 2nd input value to the Two-Complement representation (NOT + 1).