ASYNCHRONOUS DATA COMMUNICATION SYSTEM

摘要

PURPOSE: An asynchronous data communication system is to prevent the generation of a transmission error in the asynchronous transfer using a preamble. CONSTITUTION: An asynchronous data communication system comprises: a transmission FIFO(First in first out) unit(22) for the data transmission; an entry control part(21) for inputting a transmission data transmitted from a CPU(Central processing unit) into the transmission FIFO unit; a preamble ROM(Read only memory)(23) in which a preamble data is stored; a multiplexer(26) for selectively outputting either an output of the transmission FIFO unit or an output of the preamble ROM; a preamble length register(27) for deciding a length of the preamble data; a preamble counter(25) for counting a length value designated at the preamble length register and controlling the selection of the multiplexer; and a transmission FIFO control part(24) for operating the preamble counter depending on the status of the transmission FIFO unit.