The Wide-Field-Imager (WFI) instrument onboard ATHENA will be based on x-ray detectors that are read-out by frame processor modules. The core component of these modules is a Microchip RTG4 FPGA. For the last four years, the WFI team has been developing implementations that allow real-time processing of data streams. Further, we have investigated the use of softcores that can be implemented as processing units. We will present the current RTG4 design and our experiences with the design flow.