I want to use the output of a R-C integrator as a
delayed input to CPLD
(inside there is a XOR gate and counter logic). It worked OK when I use
discrete XOR IC 4070. But for same R-C values it doesn't works with
CPLD.
Is is due to the fact that analog input (sawtooth from integrator) has
given to CPLD?
Is comparator after integrator is one of the solution?
Suggest other methods for creating delays inside CPLD. That will
elliminate need of integrator. Here delay required is 1.1us.

Sonali wrote:
> I want to use the output of a R-C integrator as a delayed input to CPLD
> (inside there is a XOR gate and counter logic). It worked OK when I use
> discrete XOR IC 4070. But for same R-C values it doesn't works with
> CPLD.
> Is is due to the fact that analog input (sawtooth from integrator) has
> given to CPLD?

Yes.  It probably only worked in the CMOS version because the
parts are very slow as well as having a high threshold level.  You
should not normally provide slowly transitioning signals to digital
logic unless the logic inputs have hysteresis (Schmitt triggers).

> Is comparator after integrator is one of the solution?

As long as the comparator has a fast enough edge rate for
the CPLD.

> Suggest other methods for creating delays inside CPLD. That will
> elliminate need of integrator. Here delay required is 1.1us.

This depends on your tolerance for delay jitter.  For example if you
had
a 10 MHz clock you could use a shift register to delay 1.1uS +/- 0.1uS

Depending on the CPLD, you may have inputs with hysteresis that
would work like your original CMOS circuit.  The R-C values may need
to change to make up for the difference in threshold voltage.