The SoCWire protocol (SoCP): A flexible and minimal protocol for a Network-on-Chip

State of the art radiation tolerant SRAM-based FPGAs with large gate count offer powerful processing capability among devices qualified for space applications. Due to changing mission requirements the processing in a space instrument needs to be adaptable. Modern SRAM-based FPGAs can be partially and dynamically reconfigured and thereby offer a method of adaptability. To provide a flexible communication architecture the partially reconfigurable modules were interconnected by a SoCWire Network-on-Chip. However to map an application on this network of exchangeable hardware processing nodes in the FPGA a communication protocol is required. This paper introduces a protocol adapted to the requirements for on-chip data processing chains. The protocol is inspired by the Remote Memory Access Protocol (RMAP), but considerably simplified to limit the FPGA resource consumption for the implementation of a protocol handler, which needs to be instantiated in every single network node. Despite offloading some of the processing into dedicated hardware cores implemented on a FPGA, a data processing unit still has to feature a controlling processor. To connect the Network-on-Chip and the processor, a controlling software complements the hardware protocol handler on the processor side.