40Mhz frequency divider

Jay.slovak · Jun 2, 2005

Hi, I manged to salvage this oscilator block from one old XT PC. I have the datasheet so that is not the problem. I would like to use this as universal clock source for my PIC's :wink: . I would like to select certain frequencies using Divider, the Problem is all Ic's I have seen are limited to 30Mhz. Can you help me with this, so I can have 40,20,10,5... MHz frequencies... Thanks!

panic mode · Jun 2, 2005

use flip-flops to divide it down. the easy part is getting
20, 10, 5, 2.5, etc. (divide by two).
you can use divide_by_n chips to generate other frequencies
but beware that they won't be always simetrical.
this is perfectly ok for many cases such as counting or throttling
down clocked logic.
there are cascaded counters for this but ou can also use other logic.
for example simple FF will divide frequency by two.
if you XOR the input and output, you get 1/3 of the clock.

Jay.slovak · Jun 2, 2005

panic mode said:
use flip-flops to divide it down. the easy part is getting
20, 10, 5, 2.5, etc. (divide by two).
you can use divide_by_n chips to generate other frequencies
but beware that they won't be always simetrical.
this is perfectly ok for many cases such as counting or throttling
down clocked logic.
there are cascaded counters for this but ou can also use other logic.
for example simple FF will divide frequency by two.
if you XOR the input and output, you get 1/3 of the clock.

I know about flip-flops (D's) but my PROBLEM is the FREQUENCY... 40Mhz, are TTL's or CMOS fast enaugh???

JimB · Jun 2, 2005

Have a look at the datasheets for 74AC and 74ACT series TTL, they operate at 100Mhz +

JimB

Jay.slovak · Jun 2, 2005

JimB said:
Have a look at the datasheets for 74AC and 74ACT series TTL, they operate at 100Mhz +

JimB

Hmm one problem can be that AC or ACT series are unavailable here :cry: I can only get HC or HCT... any other solution?

40Mhz frequency divider

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40Mhz frequency divider

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