8bit aluCreated for CS63 at Earlham CollegeFor my programming project, I have chosen to simulate an 8bit ALU using Logic Sim. I came up with two designs, both of which were based on a one bit ALU, which I made into a module. designing My first design for the 8bit ALU was to simply string 8 1bit ALUs together with the carryout from from one ALU connected the carry in of the next ALU. Based on problem 14 in Chapter 3 of Tananbaum, I made a second design with the basis that the carryin to a stage is true if any two or three of the addend, the augend, or the carryin of the previous stage are true. Notice that the carryout pin on the 1bit ALU module is not used. Also notice that all the outputs are duplicated: 1 is right next to module and another one is on the left side of the diagram. This is so all the outputs can be easily seen at once. testing
I tested this new design by adding parallel bits in the A and B inputs
and checking to see if a 1 carried over into the next bit for the answer.
All bits were verified to be working correctly. You can download the actual Logic Sim files by holding the down the
mouse over a link and choosing the SAVE AS... option. Mark Stosberg's homepage

Last Modified December, 1997