The project is to create a logic block accurate replica of the classic 74181 ALU. Each section of the design uses individual logic gates along with added LEDs to provide a basic understanding of how the 74181 is implemented. The design uses 74LVC based parts which supports both +3.3V and +5V operations.
As noted in the earlier log entry (1+1 Does Equal 2 !!!!), having the signal pins on the edge of the board in the same location as the status LEDs made it pretty difficult to integrate the unit into other projects. I spent some time adding a new 1x22 header to the board to facilitate integration into projects. I decided to leave out the Pn and Gn signals since it is unlikely that this design will be used to chain multiple units together. I also had expected to go to 4 layers on the PCB to make this happen, however, it became very clear that the way the schematic and gates are laid out in a semi-bus structure that it was relatively easy to add the header. I don't know if this was an intentional result from the original designers or unintentional result of the designs optimizations... new files uploaded with prototype pictures to follow! stay tune for a new project using the Mega-One-8-One as the primary ALU!
Found some time this evening to hook up the Mega-One-8-One for testing. The Mega-One-8-One is a gate level accurate replicate of the classic 74181 Arithmetic-Logic Unit(ALU) for educational purposes. With the exception of one LED not being soldered down properly, everything is working! I ran through a series of tests and everything looks great so far! I tried to make the board layout very similar to the block diagrams that are often distributed with the datasheet for the 74181, but I am noticing that the "hook-up" using this layout is not very easy. I am going to have to think about the connectivity for the next revision. Feedback is greatly appreciated!