uses a register and some combinational logic. There is a simple state machine so you must release the button for enable_arithmetic before enabeling it again. Basically, the same operation won't happen every clock cycle 100k times a second.
Switch 6. after reset, the output should be zero. Hitting enable (Switch 5) will compute the current arithOp (+ = 2'b00, - = 2'b01, ^ = 2'b10, << = 2'b11
| # | Input | Output |
|---|---|---|
| 0 | clock | LED[7] |
| 1 | reset | LED[6] |
| 2 | enable | LED[5] |
| 3 | in_val[2] | LED[4] |
| 4 | in_val[1] | LED[3] |
| 5 | in_val[0] | LED[2] |
| 6 | arithOp[1] | LED[1] |
| 7 | arithOp[0] | LED[0] |