| 摘要 |
A transmission apparatus for half duplex communication using HDLC is provided, in which a simple logic circuit is added to a general HDLC controller to transmit a frame, adding flags before and after the frame all the time, without modification of program even when a transmission speed is changed, thereby enabling rapid and reliable communications. The transmission apparatus for half duplex communication using HDLC includes: a clock (TxC) generator, to supply it to each section of the apparatus as a synchronous clock; an HDLC controller for outputting a flag signal in a predetermined bit pattern while it does not transmit a frame signal; flag delay/detecter for outputting with delaying an output (TxD) of the HDLC controller by one byte, and outputting a flag detection signal (/Flag_detect) whenever the flag signal is detected; a CPU for outputting a transmission request signal (/Tx_Req) during a period determined with relation to the magnitude of the frame signal when data transmission is required, and sending the frame signal to the HDLC controller after a transmission ready signal (/Tx_Ready) is received; control logic for synchronizing the transmission request signal (/Tx_Req) with the flag detection signal (/Flag_detect) subsequently generated, to generate the transmission ready signal (/Tx_Ready), and to output a transmission enable signal (/Tx_Enable) determining a transmission enable time, thereby adding a desired number of flag signals (Flag) before and after the frame signal; and an output controller for sequentially encoding signals output from the HDLC controller in a predetermined code system, and outputting the encoded signals during an active time of the transmission enable signal (/Tx_Enable).
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