Dear Manan,

I forgot to tell you in my application i only wanted to indicate motion show i had conencted leds to CNTDECx and CNTDECy pins.

How can you use a multimeter to detect so narrow pulse freq. 4MHz.



Please clarify what do you mean with above.



This seems to be copied and pasted from datasheet and is correct. In simple terms whenever there is a state transistion due to movement / pulses received.

A pulse is presented on CNTDCDR. The output when idle is low but it goes high for 1/2 clock period that is 125ns with your 4MHz clock.

At the same time the U/D pin will go high if decoder is couting up this high level will remain for 125ns and then go low again. If the decoder is couting down this pin wont show any transition it will remain low during this time.

The pulses under consideration are not continous they are emitted only upon a trasistion detection for example if you a shaft rotating at 60RPM connected to 500 PPR encoder with the decoder operating in 4x mode. than you will have only 2000 transition detections in a second. so you will receive 2000 pulses in one second each having pulse width 125ns on pin CNTDCDR. In this case the effective duty cycle of pulse will be 0.00025% and this will appear as 0.00V on multimeter!!! you cant use a multimeter to measure this kind of pulses. Even the frequency option available with multimeters dont work with this kind of pulses. You need a or simillar to see these pulses.

Regards,
Prahlad Purohit