We have not tested this exactly but for your application PSoC 6 is the right choice.
>>"As far as possible, the measurement process should not use the microcontroller."
--> We think there should be some controller to process the information and tell you about exact length of the impulse easily.
For analog method, you can use the ADC inside PSoC 6 to measure the voltage on the integrator. You have to design an external circuit using integrators and MOSFETs to charge and discharge respectively. You can also use PSoC 4 to implement this method.
For Digital measurement, you can use TImer component in PSoC 6 to measure the rising and falling edges of the impulse. The problem with using PSoC 4 for this method is the maximum clock frequeny of timer is 48 MHz. So the minimum clock period is 20 mano seconds.
>>"When the generation mode pulse is activated, the PSoC produces repeated 0 - 3.3 V signals every 2s."
--> Does it mean the minimum time gap between two impulses is 2 seconds? or for every 2 seconds few impulses will be generated?
Please go through following links which might be helpful for you.