# need timing diagram help

#### needlesintheeyes

Joined Dec 4, 2007
2

Can someone show me the timing diagram or timing string for this circuit? I don't entirely understand how JK flip-flops work and I need to know for an exam and for my last lab assignment.

#### needlesintheeyes

Joined Dec 4, 2007
2

Can someone show me the timing diagram or timing string for this circuit? I don't entirely understand how JK flip-flops work and I need to know for an exam and for my last lab assignment.

the image messed up q1' connects to j2, q1 connects to k2, x connects to k1,

#### itsyaboi

Joined Nov 17, 2007
8
i am also having trouble with timing diagrams, so i instead of creating a new topic i will just post here.

let me just start by saying that i have no idea how timing diagrams work so if someone has a dummies guide to timing diagrams then tell please share because i have an exam in 3 days and i really wanna know how to do timing diagrams so i don't lose out on marks.

#### RiJoRI

Joined Aug 15, 2007
536
First, grab a data sheet. I used http://pdf1.alldatasheet.com/datasheet-pdf/view/4349/MOTOROLA/MC74HC73.html

The timing diagram shows what happens over time.
Look at the function table of the data sheet, and then apply what happens to the outputs of FF1 as the clock and X/J/K signals change to the timing diagram. Note that the outputs change on the negative edge of the clock, just as in your circuit. Since the J & K inputs are tied together, there are only two active states that we need to be concerned about: J & K HI, and J & K LO. Looking at the function table, we see that when J & K are both LO, there is no change in the outputs. BUT, when J & K are both HI, the outputs toggle: the HI output goes LO, and the LO output goes HI. (We're still dealing only with the first FF.) Copy this information onto the timing diagram. Level changes are indicated by a vertical line, and horizontal lines show the steady state levels.

Actually, there is nothing like getting a 74x73, a debounced switch for the clock, and some LEDs with resistors to see what really happens with a flip-flop!

HTH,
--Rich