A system and method is provided for phase interpolator based transmission clock control. The system includes a transmitter having a phase interpolator coupled to a master timing generator and a transmission module. The phase interpolator is also coupled to a receiver interpolator control module and/or an external interpolator control module. When the system is operating in repeat mode, the transmitter phase interpolator receives a control signal from a receiver interpolator control module. The transmitter phase interpolator uses the signal to synchronize the transmission clock to the sampling clock. When the system is operating in test mode, a user defines a transmission data profile in an external interpolator control module. The external interpolator control module generates a control signal based on the profile. The transmitter phase interpolator uses the signal to generate a transmission clock that is used by the transmission module to generate a data stream having the desired profile.