counter 0-12 rollover, DIGITAL circuits

Thread Starter

yey123

Joined Jul 20, 2008
2
I've got a problem making this circuit...

Using the combination of D FF and JK FF or 2 D FF, i have to make a circuit that will count from 0-12...

can anyone suggest something if what gates am i going to use or to add. And what connection will I make for it to function.

any suggestion will surely be appreciated,,
tnx a lot..:D
 

Papabravo

Joined Feb 24, 2006
13,453
You can't count to 12 with only 2 flipflops, never mind what type. You can only count from 0 to 3 with a pair. To count to 12 you need four flipflops. To compute this number you take the ceiling of log to the base 2 of the maximum count.
Rich (BB code):
ceil(log 12/log 2) = ceil(1.079181246/0.301029995)
 = ceil(3.584962501)
 = 4
 

Papabravo

Joined Feb 24, 2006
13,453
You could always look at a counter IC's internal logic, like a 74LS161.
True, but the internal logic won't tell him how to go from the representation of 12 back to the representation of 0. In fact a designer may design the counter so it progresses through some other sequence of states like {3,4,5,6,7,8,9,10,11,12,13,14,15}. Most counters, like the 74xx161 have a TC output that makes this kind of syncronous reload a piece of cake.
 

Papabravo

Joined Feb 24, 2006
13,453
Top