How to write directly to a GPIO Register

 I need to directly make a GPIO pin low to High within 50 nano second

when i use API




It takes 1.5 micro seconds which is a huge time for my requirement 

i have configured the TB-S1JA to operate at 48 Mhz so that i should be able to achieve 21 nano second but that is not happening 

How to toggle a GPIO with only one instruction?