Hi I have a problem reading the frequency. I want my motors to work as the frequency rises, but for my starting point to be 900HZ for example 
Where are you reading this frequency from? What code etc are you trying to use which gives you the problem?
Steve
If you have existing hardware related to the question, please provide full information on it to us.
Links to datasheets or product pages are best, full part numbers are better than nothing, pictures even.