AND8001/D

http://onsemi.com

6

Figure 6.

Q

Q

D

C

Q

Q

D

C

Q

Q

D

C

Divide By 3

50% Out

Clk in

ABC

Q

Q

J

C

E

K

Divide By 6

50% Out

D

CLK

AQ

BQ

CQ

DQ

OUT, EQ

Notice FF ”A” was chosen as the FF to drive FF ”E” in

order to align the positive edges of the clock, Divide By 3,

and divide by 6. The overall skew of the output could be

better matched if all the same type of FF and gates are used.

We already know the Divide By 3 is lockup immune,

following flow chart Figure 7 shows that the addition of the

J K does not change that situation for the Divide By 6.

Figure 7. Divide by 6 Flow Chart

011

101

100

010

000

001

111

110

The flow shows no lockup, but if one observes that the J

K is a sort of toggle device it is obvious that it can’t lock up

the counter.

The J K may need bigger input AND gates to accomplish

larger divide numbers. As an example, pick a Divide By 12

and use J K type FF’s to do the function.