An experimental synthesizable image scaler using HLS.
HLS tend to be an promising method to design digital circuits, especially for signal processing units.
First of all, HLS code usually will not have the same structure as C program code. The first thing before one start to code is structural design, which target two major aspects: communication and computation
- For a single-bit variable, use the native C++ type bool or the SystemC type sc_bit. For variables less than 64 bits wide, use sc_int or sc_uint data types. Use sc_uint for all logic and unsigned arithmetic operations. Use sc_int for signed arithmetic operations as well as for logic operations. For variables larger than 64 bits, use sc_bigint or sc_biguint if you want to do arithmetic operations with these variables. If you want to do logic operations, use sc_bv instead.
Use native C++ integer types for loop counters or when you need a variable of the size defined by the native C++ type.
Use the C++ enum for all enumerated types – for example, state variables. Use the C++ struct for all aggregate types.
It is strongly recommended that you do not use data members for storage. Use variables local to the process for all storage requirements in a process
Using Clocked Thread Processes A clocked thread process, SC_CTHREAD, is the basic unit for behavioral synthesis with SystemC Compiler
An SC_CTHREAD process uses wait statements in the SystemC code to synchronize reading from and writing to signals and ports in the process.
Each SC_CTHREAD process must have at least one wait statement. The wait(n) statement suspends process execution for n active edges of the clock. The default value of n is 1.
The outputs of an SC_CTHREAD process are modeled as being registered. When an SC_CTHREAD process writes to an output signal, the value appears after the next active edge of the clock.
When the SC_CTHREAD process is invoked, it executes statements in the process until either a wait(n) or a wait_until(cond) statement is encountered. The process is then suspended until the next active edge, or it is suspended until the next active edge where the condition of wait_until is satisfied. All variables that are local to the process are saved when the process is suspended, which means that the process state is implicitly saved. When the process restarts, execution continues at the statement that follows the wait or wait_until statement.