ALU Testing

[Jorge Bendahan]

Hi i've implemented the ALU chip, but the test failed in the second line, i can't figure out why my interpretation is wrong.

Here is a detailed info.
The second line of the ALU.cmp file has the following data (this is the correct output supplied by the authors):

|        x                  |        y                  |zx |nx |zy|ny| f  |no |       out                |zr |ng |
| 0000000000000000 | 1111111111111111 | 1 | 1 | 1 | 1 | 1 | 1 | 0000000000000001 | 0 | 0 |

If we go step by step:

Step 1: zx, Zero the X
Input:
    x = 0000 0000 0000 0000
    zx = 1

Implementation
    ***

Output step 1
    v0 = 0000 0000 0000 0000

Step 2: nx, Negate the X
Input:
    v0 (from step 1)
    nx = 1
Implementation
   ****

Output step 2
    v1 = 1111111111111111
               
Step 3: zy, zero the Y
Input:
   y = 1111 1111 1111 1111
   zy = 1

Implementation:
  ***

Output step 3
    v2 = 0000 0000 0000 0000

Step 4: ny, Negate the Y

Input:
    v2 (from step 3) = 0000 0000 0000 0000
    ny = 1

Implementation:
    ***

Output step 4
    v3 = 1111 1111 1111 1111

Step 5: Add / And
Input:
    v1 (from step 2) = 1111 1111 1111 1111
    v3 (from step 4) = 1111 1111 1111 1111
    f = 1

Implementation:
    ****

Output step 5:
//And operation is selected
   v6 = 1111 1111 1111 1111

Step 6:  Negate Output
Input:
    v6 = 1111 1111 1111 1111
    no = 1

Implementation:
***

Output step 6:
    v8 = 0000 0000 0000 0000

Step 7: If v8 = 0 then output = 1 else output = 0
Input:
    v8 = 0000 0000 0000 0000
Implementation
   ***

Output step 7: zr = 1

Step 8: If v8 < 0 then output = 1 else output = 0
Input:
    v8 = 0000 0000 0000 0000
Implementation

   ***
Output step 8:
    ng =  0
Final
    ***

[cadet1620]

Recheck the definitions of the control bits.  It often helps to work through a circuit backwards:
    out s/b 00...01,
    no is 1, therefore function output s/b 11...10 = -2,
    etc.

Also note that you can save yourself some work by hooking more that one bus/wire to an output.
    Xxx(..., out=v8, out=out);
Saves you from needing Echo16.  Figure out how to do something similar to eliminate SelBit16/Not/Not.

Once you've got your ALU working, please edit your post to remove the implementation details.  It's best not to have complete solutions posted.  People learn more by having to figure them out themselves.

--Mark

[Jorge Bendahan]

Thanks!
It was just bad wiring in one of the steps...