the solution depend on requirement of Your technology. You can read this impulse with PLC by High Speed Counter card (in the rack or ET) and value send by Profibus to next processing in the drive MM420/440.
But You have to know, that transfered value will have some delay (bus cycle, etc.)
Or You can try solve this problem via optional encoder card of Micromaster and free programmed block of MM, but You have to adapt signal voltage to max. input voltage of encoder card.
Some problems are difficult to solve without comprehensive information about them.