INTRODUCTION
The SNS Ring LLRF Control System is being designed to provide individual digital LLRF control for each of the four cavities in the ring. To date, a number of prototype and first article boards have been designed and tested, and the first integrated test of the cavity IQ control loop with the production HLRF cavity and PA was recently completed. This paper will discuss the concept and architecture of the ring LLRF system and present performance data acquired for the particular case of the cavity IQ control loop. Details of the RF related machine parameters, the theory of the ring LLRF control and the HLRF system design are found in the references [1] and [2].