Re: Confused why ALU implementation will not load on hardware simulator

Posted by WBahn on Apr 13, 2021; 12:17am
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/Confused-why-ALU-implementation-will-not-load-on-hardware-simulator-tp4035932p4035935.html

One problem you have is that you are trying to tap off an internal signal (outno[15]). This HDL doesn't support that. You can only tap the chip pins.

So if you wanted to take the least significant bit of the 16-bit output from a Mux you can't do the following:

Mux16(a=x, b=y, sel=x, out=muxout);
Not(in=muxout[0], out=tappedInverted);

You would do it like this:

Mux16(a=x, b=y, sel=x, out=muxout, out[0]=tapped);
Not(in=tapped, out=tappedInverted);

This is described in the Hardware Survival Guide that is linked at the top of the Hardware forum.