tailieunhanh - Model-Based Design for Embedded Systems- P27

Model-Based Design for Embedded Systems- P27: This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. | 226 Model-Based Design for Embedded Systems a b c FIGURE Four target configurations for productivity analysis a initial architecture b HW IDCT is attached c HW IDCT and interrupt controller are attached and d additional processor and local memory are attached. From Kwon S. et al. ACM Trans. Des. Autom. Electron. Syst. 13 Article 39 July 2008. With permission. d At first we needed to port the application code to the simulation environment shown in Figure . The application code consists of about 2400 lines of C code in which 167 lines are target dependent. The target-dependent codes should be rewritten using target-dependent APIs defined for the target simulator. It took about 5 h to execute the application on the simulator of our initial configuration Figure . The simulation porting overhead is directly proportional to the target-dependent code size. In addition the overhead increases as total code size increases since we need to identify the target-dependent codes throughout the entire application code. Next we changed the target architecture to those shown in Figure and c by using two kinds of IDCT HW IPs. The interface code between processor and IDCT HW should be inserted. It took about 2-3 h to write and debug the interfacing code with IDCT HW IP without and with the interrupt controller respectively. The sizes of the interface without and with the interrupt controller were 14 and 48 lines of code respectively. Note that the overhead will increase if the HW IP has a more complex interfacing protocol. Last we modified the task mapping by adding one more processor as shown in Figure . For this analysis we needed to make an additional data structure of software tasks to link with the run-time scheduler on each processor. It took about 2 h to make the data structure of all tasks and attach Retargetable Embedded Software Design Methodology 227 TABLE Time Overhead for Manual Software Modification Description Code Line Time h Figure