Application Of HDLC Protocol In Communication System And Realization In FPGA

HDLC is a link control protocol which based on bit. And it is often realized by ASIC devices or software. Contrasted with the two methods, we can find that the first one has the characteristics including making the design easier, good function pertinence, and reliable capability, and all of these characteristics are suitable for the mass production used for specific purpose, but it is lack of flexibility; the other method for the HDLC protocol realization is software, which is flexible, but uses more resources, the speed and the real-time character (the time-delay of signal and synchronization) can't be pre-dictated. This method can be used in other HDLC applications with few changes. For the application of HDLC in multi-signal,the occupying ratio of the processor's resource is in direct proportion to the processing routes. So the software HDLC can only be used to process low speed signal of few routes in common.This thesis includes two parts. The first part realizes the communication system which is based on HDLC protocol by two devices(MT8952 and MT9172) manufactured by Zarlink. It is designed for data transmission using twisted-pair, and can provide a link with a loop attenuation of up to 33 dB (4.0 km on 24AWG@ 160kbit/s) consisting of two 64kbit/s B-channels and one 16kbit/s signaling D-channel. The D-channel signaling information is formatted in HDLC protocol. It is mainly used to transmit controlling signals and plays an important part in data transmission. This typical application is used in a private network environment that founded behind a PABX. The HDLC Protocol Controller can be used as a D-channel interface in a digital line card comprised of multiple DNICs. The second part uses FPGA(Field Programmable Gate Array)to realize the HDLC protocol. Because of the texts of HDLC standard is more, the ASIC chip which based on special purpose can't be used in different editions and lack of the flexibility in application. FPGA adopts hardware technology to process signals, can be programmed repetitiously, and can take care of the speed and flexibility too. FPGA can processes multi-channel signals in parallel. The real-time character can be pre-dictated and emulated, so the FPGA is an appropriate choice to replace the ASIC to realize HDLC protocol function in the design of small batch communication manufactures.