ok timer or pulsin, either way, how do I know when to stop reading and start counting again?

Im reading another hall efect linear sensor datasheet: http://www.allegromicro.com/datafile/1301.pdf this one looks like more appropiate for my code, but it costs 5x the price of the one Im using

back to the HI300/D1, I don't understand how to read it from the datasheet, which by the way looks very brief.

Can you help me with some metacode on how to read this sensor?

thanks