I've finished up the final "COMPUTER" chip in Chapter 5, and it seems to work. However, when I copy it over to my own working folder to test it using all the chips I made in the earlier projects (i.e., not using any of the builtin chips) I receive the above error.
I'm trying to use the "-external" test scripts to do this testing (I copied them into my own folder too, along with their .cmp files). I was under the impression that the "-external" tests didn't use any of the builtin chips. Did I misunderstand something?
The text doesn't mention these -external scripts, so they were probably added after the text was published. In looking at them, while they don't use the ARegister and DRegister chips, it would appear that some of them assume that you are using the Screen chip since they talk about things being drawn on the screen and this is a side-effect that requires the use of that chip.
They all seem to directly twiddle the RAM16K part and that requires two things -- that it exist in the design at the right level and that it be twiddle-able. I think that latter requires the built-in version.
Whatever source you are using that talks about these -external scripts, could you copy and paste exactly what they say about it? Then I can try to see if I can understand what their purpose is and how they achieve it.
Ah, that makes sense. I used the '-external' tests on my CPU before making the "Computer" chip and I didn't have any trouble - because it's not hooked up to any memory for that test! :D
To answer your question from a few posts up, WBahn, I did some kind of search like "nand2tetris what does '-external' mean on the test scripts" and got a few threads from this forum in the results. I could probably find the exact threads in my browsing history if you really need me to, but I've looked at a lot of threads here in the last week...