High Level Synthesis

High-level synthesis (HLS), sometimes referred to as C synthesis, electronic system level (ESL) synthesis, algorithmic synthesis, or behavioral synthesis, is an automated design process that interprets an algorithmic description of a desired behavior and creates hardware that implements that behavior.

The starting point of a high-level synthesis flow is ANSI C/C++/SystemC code. The code is analyzed, architecturally constrained, and scheduled to create a register transfer level hardware design language (HDL), which is then in turn commonly synthesized to the gate level by the use of a logic synthesis tool. The goal of HLS is to let hardware designers efficiently build and verify hardware, by giving them better control over optimization of their design architecture, and through the nature of allowing the designer to describe the design at a higher level of tools while the tool does the RTL implementation. Verification of the RTL is an important part of the process.

Hardware design can be created at a variety of levels of abstraction. The commonly used levels of abstraction are gate level, register transfer level (RTL), and algorithmic level. While logic synthesis uses an RTL description of the design, high-level synthesis works at a higher level of abstraction, starting with an algorithmic description in a high-level language such as SystemC and Ansi C/C++. The designer typically develops the module functionality and the interconnect protocol. The high-level synthesis tools handle the micro-architecture and transform untimed or partially timed functional code into fully timed RTL implementations, automatically creating cycle-by-cycle detail for hardware implementation.The (RTL) implementations are then used directly in a conventional logic synthesis flow to create a gate-level implementation.