Arithmetic logic unit (ALU)
Example: Specification for a simple ALU
Function Fi = Ai Fi = not Ai Fi = Ai xor Bi Fi = Ai xnor Bi
Comment Input Ai transferred to output Complement of Ai transferred to output Compute XOR of Ai, Bi Compute XNOR of Ai, Bi
M = 0, Logical Bitwise Operations
M = 1, C0 = 0, Arithmetic Operations
F = A F = not A F = A plus B F = (not A) plus B
Input A passed to output Complement of A passed to output Sum of A and B Sum of B and complement of A
M = 1, C0 = 1, Arithmetic Operations
F = A plus 1 F = (not A) plus 1 F = A plus B plus 1 F = (not A) plus B plus 1
Increment A Twos complement of A Increment sum of A and B B minus A