ComputerRect.tst failing

[Shmeegoose]

My computer implementation passes all other Computer tests. It also passes the external version of ComputerRect.tst althought doesn't actually display anything. From browsing around through other posts I noticed that there may be updated versions of the CPU and Memory tests I should run which may catch corner cases.

It fails on line 5 and when I look at the ComputerRect.out it shows that the DRegister reads 0 when it should be 4, other than that everything is correct.

I didn't want to post code without first getting permission. Let me know if I should post my Memory and CPU code or email it somewhere. Thanks! Having an absolute blast with this course. Been recommending it to everyone.

[WBahn]

The first step is to be sure you understand (and agree with) the test. Look at the test script and start with the inputs that determine the results on line 5 and walk through what the outputs should be (based on the specified behavior) for the D Register. Do you agree that it should be 4. Now walk through your design, very carefully and deliberately, and see if you agree that it is actually producing a value of 0 instead. Now you are in a position to consider why it should be 4 and why it actually is 0.

[Shmeegoose]

Thanks for the reply!

After holiday break I'm back to wrap this up.

I was able to resolve the issue. It turned out that the load signal for my D register wasn't configured correctly.

I recommend adding a test case to the CPU.tst that exercises the D register load logic in greater detail to catch this issue before seeing the failure at the computer level. Though it does make for a fruitful debugging exercise.

[nblackburn]

I just had the same issue and the problem was also my D register's load signal in my CPU implementation. However I still do not understand how to look at the test script and see what the outputs should be. Could you please elaborate further? I wish to understand how to debug this problem using your post!