Logic circuit? - Page 1
Forum section: electronics / beginners

author: etstudent
author_rank: Regular Contributor
timestamp: October 16, 2012, 10:02:40 pm
content: I DO NOT want the answer, just point me in the right direction, I'm a bit lost here. I'm not great with logic circuits to begin with. Let me know if the file opens too? Thanks for any help.Moderator: Resized image to be readable

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 16, 2012, 10:15:37 pm
content: Work from back to front, fill in the 1's or 0's that make it happen...

author: etstudent
author_rank: Regular Contributor
timestamp: October 16, 2012, 10:22:37 pm
content: Thanks, that is good advice.

author: etstudent
author_rank: Regular Contributor
timestamp: October 17, 2012, 01:06:23 am
content: I believe its 011110, am I correct?

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 17, 2012, 07:43:23 am
content: Quote from: etstudent on October 17, 2012, 01:06:23 amYup, I have to agree.

author: Psi
author_rank: Super Contributor
timestamp: October 17, 2012, 07:46:11 am
content: yep, that's what i get too

author: Jimmy
author_rank: Regular Contributor
timestamp: October 17, 2012, 08:34:52 am
content: D

author: psycho0815
author_rank: Regular Contributor
timestamp: October 17, 2012, 10:41:01 am
content: Maybe i'm missing something, but since when does a nibble have 6 bits?

author: rolycat
author_rank: Super Contributor
timestamp: October 17, 2012, 11:05:19 am
content: Quote from: psycho0815 on October 17, 2012, 10:41:01 amI'm guessing the individual setting the question was a bit 'old school' - once upon a time nibbles could have more than four bits. Similarly, bytes weren't always eight bits long. Some early mainframe computers had a 36-bit word length, and a byte could be nine bits, or even six.

author: GeoffS
author_rank: Unknown
timestamp: October 17, 2012, 11:23:15 am
content: Quote from: rolycat on October 17, 2012, 11:05:19 amVery old school! The first computers I worked on (Univac 1108) were 36 bit word with ASCII characters taking either 9 bits (1 bit ignored) or 6 bits (upper case letters only). The term byte wasn't used.

author: rolycat
author_rank: Super Contributor
timestamp: October 17, 2012, 12:21:22 pm
content: Quote from: GeoffS on October 17, 2012, 11:23:15 amWell, the 6-bit characters used an encoding called Fieldata, not ASCII, which has always featured lower-case characters.QuoteNot by Univac - they called them quarter words or sixth words. However, IBM and DEC also had 36-bit machines. The DEC PDP10 had byte instructions for which the byte could be any length between 1 and 36 bits.OK, I admit it - I'm a bit old-school, too.

author: etstudent
author_rank: Regular Contributor
timestamp: October 17, 2012, 12:25:18 pm
content: Thanks guys, I appreciate the help and info. I'm glad I came up with the right answer. What exactly are nibbles, just a bit of the code that turns on the circuit? Do you use this often in the field? I'm having trouble with gates, truth tables, and this kinda stuff. AND, OR, NOT, NAND, and the rest just confuses me. Makes me nervous if I get a job working with linear circuits.

author: psycho0815
author_rank: Regular Contributor
timestamp: October 17, 2012, 12:30:28 pm
content: Quote from: GeoffS on October 17, 2012, 11:23:15 amThanks, i didn't know that. guess I'm too young...

author: Bored@Work
author_rank: Super Contributor
timestamp: October 17, 2012, 01:55:59 pm
content: Quote from: etstudent on October 17, 2012, 12:25:18 pmOne half of a byte. I.e. in these times of eight bit bytes a nibble is four bit.And when run into the term "octet", that is another name for an eight bit byte, born when bytes weren't by default eight bit.

author: etstudent
author_rank: Regular Contributor
timestamp: October 17, 2012, 03:03:31 pm
content: Thanks, appreciate the info. Is this something used a lot in the field?

author: SeanB
author_rank: Super Contributor
timestamp: October 17, 2012, 03:38:27 pm
content: I worked on serial word machines, where a word was up to a 16 bit number, but could be variable length depending on where it was used. Mostly because the storage was a pair of shift registers of limited length, MK4007 cmos shift registers. They had their own supply rails.............

author: Bored@Work
author_rank: Super Contributor
timestamp: October 17, 2012, 05:05:27 pm
content: Quote from: etstudent on October 17, 2012, 03:03:31 pmOctet is typical for telco stuff. They still love to distinguish between the well defined octet and the once only vaguely defined byte. The rest of the world moved on and uses byte for eight bits, unless explicitly specified differently.Nibble is used when you need it, i.e. when you need to talk about half a byte. Which is not too often. One case is when you do packed BCD numbers.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 17, 2012, 06:06:16 pm
content: @etstudent:Hard to answer if you delete the post

author: etstudent
author_rank: Regular Contributor
timestamp: October 17, 2012, 06:19:34 pm
content: Sorry the picture would not post, file too large, but its the same thing i did yesterday and it posted fine. Let me try again.Moderator: The picture posted OK but it was too large to be viewable by most people. Your latest image, while smaller, is also bigger than necessary. Try to keep images to less than 1200x800 or so. I've resized this one to 1024x768 and it is still readable.What would be the outputs of this circuit if the inputs are 010011 and 101000?Thanks for any help. I think its 1,1 right now? What do you think of the question overall?

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 17, 2012, 07:28:01 pm
content: I see 3 AND ports which will only output a 1 if both inputs are 1The bottom 2 AND ports will never output a 1 because you will need 11XXXX or XX11XX for that.The upper AND port is followed by an inverter, so to get a 1 at the input of the last OR port (pin 1) you need a 0 at the output of the upper AND.This will happen when the input is not 11, so for 101000.My answer would be C. 0,1

author: andersm
author_rank: Super Contributor
timestamp: October 17, 2012, 09:24:11 pm
content: Quote from: Bored@Work on October 17, 2012, 05:05:27 pmYou'll also run into the word if you work with French people, as that's what they use for byte.

author: etstudent
author_rank: Regular Contributor
timestamp: October 17, 2012, 11:38:25 pm
content: Thanks PA0PBZ, appreciate the help. I have one or two more that I'm gonna post soon. I want to master this.

author: etstudent
author_rank: Regular Contributor
timestamp: October 18, 2012, 02:42:14 am
content: For that same circuit I have another question. The outputs would be for inputs of 111111 and 000000?Is it not 0,0? or 0,1? My guess now is 0,0. thanks for the help.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 18, 2012, 05:08:02 pm
content: I'd say 1,1 but this time you prove it

author: etstudent
author_rank: Regular Contributor
timestamp: October 18, 2012, 05:49:02 pm
content: Quote from: PA0PBZ on October 18, 2012, 05:08:02 pmHonestly these logic gates and logic circuits confuse me so bad I'm not sure. This is the one part of my program that just confused me very bad. Thanks for the help though, I appreciate.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 18, 2012, 08:16:00 pm
content: It's not really that hard, but if I just give you the answer you will not learn anything.So, I filled in the first step, can you do the outputs?

author: HardBoot
author_rank: Regular Contributor
timestamp: October 18, 2012, 08:28:54 pm
content: Really easy logic questions, I figured them out in my head, if you can't do homework this simple just use logisimhttp://ozark.hendrix.edu/~burch/logisim/

author: etstudent
author_rank: Regular Contributor
timestamp: October 19, 2012, 05:02:26 pm
content: Thanks for the help guys, appreciate every bit of it.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 19, 2012, 06:10:09 pm
content: Quote from: Electroalek on October 19, 2012, 05:34:57 pmNot sure what you are talking about right now...

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 19, 2012, 06:34:03 pm
content: Quote from: Electroalek on October 19, 2012, 06:14:38 pmWell, the inputs are there (all 1's) and there is only one output, so I still don't understand your answer of 0,1.