Hi I need to create a VHDL adder/subtractor structually using ripple carry. I'm fairly new to this and it is for a university course. The problem is that I don't know how to do the subtracting mechanism. I was provided with a testbench, so I can't change that. I added the files to attachment. Thank You
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> The problem is that I don't know how to do the subtracting mechanism. Good news: you already implemented the subtractor. You just have to remove the lousy faults and syntax errors reported to you (in numbers around 15-20) and then the thing is working... A little hint: all of the errrors are in the adder_subtracter.vhd
Haha, there were many errors, I don't know how when I first compiled it, I didn't notice them or how it even got to the simulation. It now doesn't give me any errors at compiling. But it doesn't work still, I don't know what to make of these characters in a_tb and b_tb ( c, d, f etc.). I attached the corrected versions in to the attachment. And thank you for your fast reply
> But it doesn't work still, No, its ok. All is fine. Your waveform is exactly like mine! The only remaining problem ist this: > I don't know what to make of these characters ( c, d, f etc.). To understand the waveform have a look for hexadecimal numbers and their binary representation, and then how a adder of 4 bits width reacts when there is an overflow, and also how a subtractor reacts when there is an underflow...
Ok, I read about those things. After analyzing the graph I do too realize that it is working. Anyways, I really appreciate that You took the time to help me.
I have problem with test bench . He doesn't work . What is problem? I also have full addder file but i didn't attach
> He doesn't work . What is problem? The major problem is, that you don't tell us, what the problem is. So: what is going wrong? What does the simulator say? The second most problem is that you hijacked a thread... :-/