thanx all people the counter part is done... now i need to multiply 215 by .000, .001, .010, .011, .100, .101, .110, .111 for the duty cycles 0, 12.5% , 25% , 32.5% , 50% , 62.5% , 75% and 87.5%.. do i have to use a 8 x 3 multiplier?? i am having a problem with the decimal point

 

or i have to use FP Multipliers ?? if yes which one?

 

I would have though that you must include the 0 bits also. Thinking about it more carefully, it appears that the solution is valid so long as you are counting up from zero.

That's right. The cheap-and-cheerful way to turn a 4040 (or any up-counter with binary outputs) into a divide-by-n is to use a diode AND gate on the outputs that need to be 1, and feed the gate output into the +RESET input.

 

im now using two dm74ls193n to connect them together do i have to connect pin 12 of one to pin 13 of the second?? or pin 12 of one to clock of 2nd... and for stopping the counter at 215 instead of letting it go to 255 shouldnt i be using a and gate instead of a nand gate as the clear pin works at logic 1??

From the datasheet:

The counters can then be easily cascaded by feeding the
borrow and carry outputs to the count down and count up
inputs respectively of the succeeding counter.

Inverting the output of the AND (NAND) would work for the reset, but it would need to clear both counters.