"Coding" a chip

[mbm29414]

I'm working on implementing the Bit chip from Chapter 3.

I kinda understand the chip diagram, but I couldn't figure out where to start the HDL code.

I looked at the hints you guys gave in another post and still was unable to get started.

So, I looked up a "cheater" on Google Code. Honestly, after seeing it, I don't think I ever would have considered the solution (even though it was a wrong implementation).

I don't want to give it away too much, but did I simply miss the fact that you can wire the "in" pin of a chip to an internal pin that doesn't have a value at the time?

I've got my chip built (fixing the mistake in the "cheater") and it passes the test, but I still can't really figure out how it works.

I'm a Visual Basic .NET developer, and it just doesn't make sense to me to be able to pass IN a variable that doesn't exist yet. Can someone explain that to me?

[cadet1620]

mbm29414 wrote

I'm a Visual Basic .NET developer, and it just doesn't make sense to me to be able to pass IN a variable that doesn't exist yet. Can someone explain that to me?

The trick here is that you are not writing a program; you are connecting wires together.  See Helpful HDL philosophy

--Mark

[mbm29414]

Well, so I read your helpful HDL document; I hadn't realized before that this wasn't programming.

I now realize that I can simply draw the diagram and label each wire, making sure that those wires are the input and output of the correct chips as I "design" the chip in HDL.

That really makes the whole concepts of Chapters 1, 2 and 3 come alive and into focus a lot more for me.

Thank you for that bit of knowledge.

I have to admit, though, that's it still weird for me to think that order doesn't matter. I could completely reverse the order of my ALU and it still works? <Shudder />

(And, yes, I now realize that I put my user name where the topic title should have gone. D'oh! I've tried changing the subject; if a moderator reads this, "Coding" a chip is a better title for this post. Might be more useful to others that way.)

[cadet1620]

mbm29414 wrote

I have to admit, though, that's it still weird for me to think that order doesn't matter. I could completely reverse the order of my ALU and it still works? <Shudder />

Or randomize the order of the parts.  PC boards don't care what order you solder in the parts.  Building the PCB and using it are completely different operations .