Development Of Cable Modem With Compressed Code And Startup Function

Recently, high-speed broadband access technology has become the front line and focus of communication technology field People are not satisfied with traditional data service any more, and the demand of broadband Integrated Service is being increased rapidly. Traditional dialing technology has become the bottle-neck of whole traffic network. It is a problem to urgently resolve how to open the last kilometer of "information high-speed road". HFC broadband access network is an effective solution to the problem. Cable Modem is the terminal device of HFC broadband access network.The size of Cable Modem application program is becoming larger and larger as the function of Cable Modem is enhanced and the program language has turned to C++, which demands larger memory. So there is a problem to solve, that is how to implement compressed code with startup in the existing hardware.This article is the research on the above problems. Main research is as the following:First, this article analyses the principle of Cable Modem,and the hardware structure which is made of Motorolar's 32-bit embedded microchip-computer MPC850 and Broadcom's BCM3300 ASIC. Then the chip BCM3300 is fully described and the Cable Modem's running and developing platform is introduced to develop the software of Cable Modem.Second, due to the fact that Cable Modem is a typical embedded system, data compressing algorithm is introduced. To implement compression startup of Cable Modem, the decompression algorithm must be fairly quick and needs little memory. Then the compression algorithm, decompression code, startup code are provided. The basic principle of compression startup is described as follows: the application program image is developed and compressed on host machine, then it is downloaded to flash through programmer. During compressing, the decompression address should be pointed out. On target machine, a decompression code is added into the bootloader. When program is running, it would detect compressed image in flash, and then decompress it to SDRAM,pointer should point to the decompressed code, and then executes it. Thus the compression startup of Cable Modem is implemented.It is indicted from experiment results that Cable Modem can implement the same function but its flash memory size can be reduced 1/2. However the startup time doesn'tincrease much. As Cable Modem is a typical embedded system, the data compression algorithm and software can be used by other embedded system directly. In a word, the startup compression technology can save the memory cost of embedded system, and assure that the function-enhanced compressed image can run in the existing hardware in the future time...