In this paper, we introduce a new efficient register transfer level (RTL) method to develop on-line self-test routines. We consider some prioritizations to select the components and instructions of the processor. In addition, we choose test patterns based on spectral RTL test pattern generation (TPG) strategy. For the purpose of spectral analysis, we use the wavelet transform. Also, we use a few extra instructions for the purpose of the signature monitoring to detect control flow errors. We demonstrate that the combination of these three strategies is effective for developing small test programs with high fault coverage in a small test development time. In this case, we only need the instruction set architecture (ISA) and RTL information. Our method not only provides a simple and fast algorithm for on-line self-test applications, also gains the advantages of utilizing lower memory and reducing the test generation time complexities in comparison with proposed methods so far. We focus on the application of this approach for Parwan processor. We develop a self-test routine using our proposed method for Parwan processor and demonstrate the effectiveness of our proposed methodology for on-line testing by presenting experimental results for Parwan processor.