hobby servo motor interface with 8051 microcontroller

[pdsherathia]

i tried to interface a hobby servo motor with 8051, the control pulse is connected with 8051 via buffer 74ls244. the center position of motor is at 1500 microseconds pulse width of control bit.
when i give 1500 microseconds it vibrates abt center position, when i increase pulse width to 1750 it doesn't change position whereas it should move to new position. also when i decrease pulse width to 1250, it doesn't change position.
suggest me better option of running this motor.

[kam]

there is no other option. only to make sure that the frequency of the pulses is in the nominal area, usually around 50 hz