Communication network

A communication network in which a plurality of stations are connected by a loop-shaped transmission path, any one of the plurality of stations functioning as a master station, and capable of performing asynchronous data communication not requiring real time transfer and isochronous data communication requiring the real time transfer, wherein:

• the plurality of said stations are assigned actual IDs which are used in said asynchronous data communication and not overlapped with each other;
• said master station sends out to said transmission path an inquiry token packet for inquiring whether each of said stations has a communication request of said asynchronous data;
• said inquiry token packet is received by each of said stations through being transmitted on said transmission path without being changed by each of the stations;
• each of said stations sends out, provided that it holds said asynchronous data and the actual ID of a station to be a recipient of the asynchronous data when receiving said inquiry token packet transmitted through said transmission path, the communication request of said asynchronous data and the actual ID of the station to be the recipient of the asynchronous data to said transmission path using a slot previously assigned thereto;
• said master station sends out to said transmission path a token packet for said asynchronous data communication in which a station to be a source of transmission of the asynchronous data and the station to be the recipient of the asynchronous data are designated using said actual IDs on the basis of the communication request of said asynchronous data and the actual ID of the station to be the recipient of the asynchronous data received through said transmission path;
• said token packet for asynchronous data communication is received by each of said stations through being transmitted on said transmission path without being changed by each of the stations;
• wherein each of said stations:
• analyzes the token packet for asynchronous data communication received through said transmission path;
• sends out, when being designated as the source of transmission of the asynchronous data in the received token packet for asynchronous data communication, an asynchronous data packet held therein to said transmission path;
• and
• receives, when being designated as the recipient of the asynchronous data in the received token packet for asynchronous data communication, the asynchronous data packet sent out to said transmission path;
• and
• wherein said asynchronous data packet does not include the actual IDs assigned to the stations to be the source and the recipient thereof.

In a communication network in which a plurality of stations are connected by a loop-shaped transmission path, any one of the plurality of stations functioning as a master station, and the stations other than the master station functioning as slave stations, and capable of performing asynchronous data communication not requiring real time transfer and isochronous data communication requiring the real time transfer, a method of setting actual IDs, in the stations, which are not overlapped with each other, wherein:

• each of the slave stations is previously assigned an initial ID common at least among the slave stations;
• each of the slave stations comprise a switch for switching between connection and disconnection of the transmission path;
• the master station sends out to the transmission path a token packet for switching which is receivable by the slave stations having the initial IDs, and then sends out to the transmission path a plurality of actual ID setting commands for respectively setting the actual IDs which differ from each other in the slave stations;
• each of the slave stations disconnects the transmission path using the switch when having the initial ID and also receiving the token packet for switching sent out by the master station so that a receiving signal is not transmitted to the station positioning on the downstream side of the slave station on the transmission path;
• each of the slave stations sets therein, when having the initial ID and also receiving through the transmission path the actual ID setting command sent out by the master station, the actual ID on the basis of the received actual ID setting command;
• each of the slave stations connects the transmission path using the switch when the actual ID is set therein so that the subsequent actual ID setting command coming through the transmission path from the master station is transmitted to the station positioning on the downstream side of the slave station on the transmission path;
• the actual IDs are thus successively set in the slave stations, starting from the slave station positioning on the downstream side of the master station and nearest thereto;
• the master station sends out to the transmission path a token packet including the actual IDs of the stations to be a source of transmission of data and a recipient thereof in the isochronous data communication or the asynchronous data communication;
• the token packet is received by each of the slave stations and the master station through being transmitted on the transmission path without being changed by each of the slave stations;
• and
• each of the slave stations and the master station:
• analyze the actual ID of the token packet received through the transmission path;
• send out, when being designated as the source of transmission of the data in the analyzed token packet, a data packet held thereby to the transmission path;
• and
• receives, when being designated as the recipient of the data, the data packet sent out to the transmission path;
• and
• wherein the data packet does not include the actual IDs assigned to the stations to be the source and the recipients thereof.