The hardware design and software programming of the RS_485 communication is completed based on the TMS320VC5402 DSP.In order to extend the hardware,designer connects directly the multi-channel buffered port(McBSP) of Texas Instrument's TMS320VC5402 DSP chip by the SPI mode with MAXIM's MAX3100 universal asynchronous serial transceiver interface,and then get through Linear Technology's LTC1480 which is a low power RS_485 transceiver,thus achieve a new standard interface based on RS_485 serial communication.The design makes full use of the DSP on-chip resources to simplify the hardware and software architecture as much as possible.The paper presents a hardware connection principle diagram and introduces related software programming.