Full adder 8 bits first draw schemati - Page 1
Forum section: electronics / projects

author: Spartatux
author_rank: Newbie
timestamp: February 22, 2015, 01:15:48 pm
content: I have no formation in electronic, I do that project as a hobby.This is my first pcb project and this is the first part of a bigger project.So there is the schematic, please comment, let me know if I did a mistake and/or if I can improve it.I used EaglePCB.Thank you

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 22, 2015, 01:52:40 pm
content: Label every net, that way you can make shure you connected the right one.Keep the "wires" straigt and short, there are many 90° bends in there that do not need to be there.Something funky is going on at the output of IC3A, that junction should not be there.Run the ERC to get possible problems.JP2 has a missing connection on PIN4, my guess is, that should be that way.You could Flip/Mirror components to minimise the wire cross routing, to me that makes it more readable but the downside is that the pins are not at the same location on every component.For example, if you mirror IC3A along the horizontal axis, you can move IC5B over the junction between IC2A and IC3A.The same for all the other gates down the line.There are no decoupling caps in there, every IC should have one close to the supply pin on the PCB.Upload the Eagle file next time along with the PNG

author: Spartatux
author_rank: Newbie
timestamp: February 23, 2015, 04:38:40 am
content: Thank youit's exactly the kind of answer I was looking for.I will try to make the modification you suggest during the week and I will post my progress.I attached my project.

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 23, 2015, 10:29:26 am
content: Quote from: Spartatux on February 23, 2015, 04:38:40 amThat is not how decoupling caps work in this setup

author: Spartatux
author_rank: Newbie
timestamp: February 23, 2015, 12:40:22 pm
content: Well, like I said in my first post, I have no formation in electronic, I know approximately what decoupling caps mean, but it's about it. So can you please explain a little bit more?Thank youUpdate: Ok, I search "decoupling caps" on google and now I get it, I think...

author: Spartatux
author_rank: Newbie
timestamp: February 24, 2015, 04:55:00 am
content: I did a lot of modifications, it's not finish, but it's much more clear I think.What do you think?

author: BlueBill
author_rank: Regular Contributor
timestamp: February 24, 2015, 05:58:56 am
content: May I as why you're building a half-adder? What's the bigger project?

author: Spartatux
author_rank: Newbie
timestamp: February 24, 2015, 12:32:52 pm
content: It's a full-adderAnd my full project is a 8 bits CPU.But there is a lot of part of CPU that I have no idea how they work right now.So I start with what I know adder, and, or, xor, ALU, and I will try to figure out the other parts once I am there.

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 24, 2015, 04:18:16 pm
content: Quote from: Spartatux on February 24, 2015, 04:55:00 amLooks about good. But please be advised that i dit not check the function of the circuit, just the astetics. I am not that good with hard wired logic.The bypass caps are wired the right way this time aroundI had a quick poke around, i do not know if i made it worse but you can wire the carry lines straigt between the gates if you flip them arround and mirror, have a look at the atachment.

author: Spartatux
author_rank: Newbie
timestamp: February 25, 2015, 12:27:20 am
content: Don't worry about the logic, I get that part.Did some modification again and I think it's pretty much it for the schematic.Next step: routing.

author: Spartatux
author_rank: Newbie
timestamp: March 22, 2015, 06:37:55 pm
content: Hi,I have done the routing(no auto-routing), can you give your impressions(trace size, routing, decoupling caps, etc)?Thank you