The adder/subtracter or logic unit output is a function of control and data inputs (see Figure 1). The data inputs to the adder/subtracter are selected by the OPMODE and the CARRYINSEL signals. The ALUMODE signals choose the function implemented in the adder/subtracter. Thus, the OPMODE, ALUMODE, and CARRYINSEL signals together determine the functionality of the embedded adder/subtracter/logic unit. When using the logic unit, the multiplier must not be used. The values of OPMODEREG and CARRYINSELREG must be identical.
As with the input multiplexers, the OPMODE bits specify a portion of this
function. The symbol
± in the table means either add or subtract and is
specified by the state of the ALUMODE control signal. The symbol
the table means concatenation. The outputs of the X and Y multiplexer and CIN are always
added together. For more information, refer to ALUMODE Inputs.