A reconfigurable real-time SDRAM controller for mixed time-criticality systems

Verifying real-time requirements of applications is increasingly complex on modern Systems-on-Chips (SoCs). More applications are integrated into one system due to power, area and cost constraints. Resource sharing makes their timing behavior interdependent, and as a result the verification complexity increases exponentially with the number of applications. Predictable and composable virtual platforms solve this problem by enabling verification in isolation, but designing SoC resources suitable to host such platforms is challenging. This paper focuses on a reconfigurable SDRAM controller for predictable and composable virtual platforms. The main contributions are: 1) A run-time reconfigurable SDRAM controller architecture, which allows trade-offs between guaranteed bandwidth, response time and power. 2) A methodology for offering composable service to memory clients, by means of composable memory patterns. 3) A reconfigurable Time-Division Multiplexing (TDM) arbiter and an associated reconfiguration protocol. The TDM slot allocations can be changed at run time, while the predictable and composable performance guarantees offered to active memory clients are unaffected by the reconfiguration. The SDRAM controller has been implemented as a TLM-level SystemC model, and in synthesizable VHDL for use on an FPGA.