An improved external controller with dual microcontrollers useable with an implantable medical device is disclosed. The external controller comprises a low speed (low frequency) microcontroller and a high speed (high frequency) microcontroller. The low speed microcontroller receives telemetry data from the medical device, converts data into graphical commands, and transmits commands to the high speed microcontroller. The high speed microcontroller interprets the graphical commands, retrieves images indicative of the commands from a storage device, and renders the images onto a display screen. The high speed microcontroller may also process more complicated data sent from the low speed microcontroller, and return the results to the low speed microcontroller to allow it to form the graphics command for the high speed microcontroller to execute.
