Design Of Data Link Layer In PCI Express

PCI-Express (3GIO) as the third generation of universal I/O interconnect, leads to a revolution. It is not only PCI compatible, but also can enhance the performance of the existent device. The key PCI-Express attributes are: high performance, support multiple platforms interconnect, high reliability, easy for upgrade and low cost. Today the software is becoming more and more dependent on the hardware platform, especially the I/O subsystem. There are usually a mass of data that from the video or audio source to be processed, sometime they even need to be real time processed. PCI-Express can not only satisfy the requirement of huge I/O bandwidth, but also can be applied to desktop system, mobile system, server, communication system, work station and embedded system brilliantly.Without doubt that the PCI-Express is an advanced technology, the research and implement of PCI-Express are making sense and valuable. But the PCI-Express related research and development are mainly in foreign country now, so there are few referenced information, therefore it is quite difficult to accomplish the hardware implementation. The process covers the front-end and back-end part of IC design;it needs certain IC design experience.Data Link Layer (DLL) acts as an intermediate stage between the Transaction Layer (TL) and the Physical Layer (PL). Its primary responsibility is to provide a reliable mechanism for exchanging data. The amount of coding is quite big, especially in the data path, it exists the problem of arbitrating multi-path data, the design style is approved to having big influence on the performance, from the performance standpoint, the calculation of CRC can not accept the bit operation way, but when using the multi-bit way, it should consider the circuit delay problem. The circuit should be designed aboratively to avoid big delay path which will make synthesis fail. The ACK/NAK mechanism and the flow control mechanism have great influence on the performance, so based on the implementation of DLL it's also important to consider of increasing performance.