4 bit Op Code ALU. OpCodes are as follows-
0000 AND
0001 OR
0010 NOT
0011 XOR
0100 NAND
0101 NOR
0110 XNOR
0111 Addition
1000 Subtraction
1001 Multiplication
1010 Compare
1011 Shift L Logically
1100 Shift R Logically
1101 Shift L Arithmetically
1110 Shift R Arithmetically
1111 Running Sum
Running Sum takes the current 4bit number at the input and continously adds it to the output every second.
Compare is 2'b10 when A is greater than B, 2'b01 when B is greater than A. 2'b11 when equal.
NOT treats A and B as a combined 4bit input.
Subtraction anticipates am unsigned number input (treats them as positive numbers essentially) however will give signed output depending on the operation. It acts as A-B.
Testing can be done by connecting the outputs to LEDs and treating them as an 8 bit output. Seeing how they correspond to the selected OpCodes and inputs.
an external circuit with LEDs or a BCD converter to represent the numerical outputs
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | OpCode 0 | segment a | Output bit 0 |
| 1 | OpCode 1 | segment b | Output bit 1 |
| 2 | OpCode 2 | segment c | Output bit 2 |
| 3 | OpCode 3 | segment d | Output bit 3 |
| 4 | B 0 | segment e | Output bit 4 |
| 5 | B 1 | segment f | Output bit 5 |
| 6 | A 0 | segment g | Output bit 6 |
| 7 | A 1 | dot | Output bit 7 |