# Finding next state equation for UV flip flop?

Discussion in 'Homework Help' started by Gonzalo Armbrust, Oct 28, 2015.

1. ### Gonzalo Armbrust Thread Starter New Member

Jun 28, 2015
16
0
"A M-R flip-flop behaves as follows:
If MR = 00, the flip-flop does not change state.
If MR = 10, the flip-flop is reset; i.e. Q=0.
If MR= 11, the flip-flop changes state.The input combination
MR = 01 is not allowed.
Give the next state equation for this flip flop"

I have no idea how to solve this, could anyone provide any hints / clarifications that might help me out?

2. ### WBahn Moderator

Mar 31, 2012
17,748
4,796
Is this a "UV" flip flop or a "M-R" flip flop?

Look at the next state equations for a JK flip flop. The idea is very similar.

3. ### Gonzalo Armbrust Thread Starter New Member

Jun 28, 2015
16
0

It's an M-R flip flop, I apologize that was a typo. I have worked out a table for the solution and I think I may have gotten it:

x's are labeled as don't cares

M | R| Q | Q(+)
x 0 0 0
------ 0 1
1 x 1 0
0 0 1 1

when Q and Q(+) are both set to zero, this satisfies the condition in which MR = 00 and when MR = 10, since Q and Q(+) does not change state, and it also "resets" to 0, so m could be either 1 or 0, or just labeled as a don't care. The case of 01 is ignored since it is not allowed. The conditions are reversed for when Q = 1 and Q(+) = 0, this means MR = 10 and also equal to 11 since the values compliment. At Q and Q(+) = 1, MR has to be equal to 00 since it does not change state...

is this correct?

4. ### WBahn Moderator

Mar 31, 2012
17,748
4,796
I have no idea what the line in your table is that has all the hyphens.

Using TABLE tags might help.

You are talking about Q(+) as thought it is one of your inputs.

Your table doesn't cover the case where MR = 11 and Q = 0.

5. ### Gonzalo Armbrust Thread Starter New Member

Jun 28, 2015
16
0

the line with the hyphens I used to show that the case in which MR = 01 is not allowed in the problem. For a certain part, I was asked to fill out the corresponding characteristic table with the correct MR inputs, so I was given:

// MR are left blank for me to fill out

Q | Q(+) | M | R
0 | 0 | |
0 | 1 | |
1 | 0 | |
1 | 1 | |

I don't know how to use table tags.

Since I was given this specific table to fill out, I need to find the U and V inputs that satisfy these conditions, so for example M = 0 and R= 0, when Q is 1 and Q(+) is 1, since the state does not change from Q, to Q(+). Would my table be correct for these circumstances?

6. ### WBahn Moderator

Mar 31, 2012
17,748
4,796
What are these 'U' and 'V' inputs that you keep talking about?

7. ### Gonzalo Armbrust Thread Starter New Member

Jun 28, 2015
16
0

Nevermind! I solved it earlier today. Thank you for the help