Ring network with temporary master node for collecting data from slave nodes during failure

A communication network comprising a ring transmission line and a plurality of network nodes interconnected by the line, one of the nodes acting as a master node and having master memory, and each of the other nodes acting as a slave node and having a memory, said slave nodes having different priorities,

• said master node including means for successively sending a first command message containing data stored in the master memory to each of the slave nodes in a descending order of said priorities, receiving response therefrom, and updating the master memory with the response message, said response message indicating particular information of the slave node,
• each of the slave nodes comprising:
• receive means for receiving signals from said transmission line;
• means for updating the memory of the slave node with the contained in the first command message if the same is received by said receive means, and returning the response message of the slave node to the master node;
• means for successively sending a second command message containing data of the memory of the slave node to a different one of the slave nodes if the first command message is not received until said second message is received by said receive means from a slave node whose priority is higher than the priority of the sending slave node, and updating the memory of the sending slave node with said response message returning from each slave node, the data contained in a subsequent transmission of said second command message being a version of the data updated by a response message returning in response to a previous transmission of said second command message;
• and
• means for returning the response message of the slave node on receiving said second command message from a slave node whose priority is higher than the priority of the slave node.

In a communication network comprising a ring transmission line and a plurality of network nodes interconnected by said line, one of said nodes operating as a permanent master node having a master memory and generating a first command message containing data stored in the master memory, and each of the other nodes having a memory and operating as a temporary master node for generating a second command message containing data stored in the memory thereof, or as a slave node for generating a response message in response to the first or second command message indicating particular information of the slave node, a method comprising the steps of:

• a) at said permanent master node, successively sending said first command message from said permanent master node to each of the slave nodes, and updating the master memory with said response message returning from the slave node;
• b) at each one of said slave nodes, determining whether said first command message is received or not;
• c) if said first command message is determined to be received, updating the memory of the slave node with the data contained in the first command message, and returning said response message from the slave node to said permanent master node;
• d) if said first command message is determined to be not received, operating the slave node as said temporary master node by sending said second command message to a different one of other slave nodes;
• e) updating the memory of the temporary master node with said response message returning from said one slave node;
• and
• f) repeating the steps (d) and (e).

In a communication network comprising a ring transmission line and a plurality of network nodes having different priorities interconnected by said line, one of said nodes acting as a permanent master node having a master memory and generating a first command message containing data stored in the master memory, and each of the other nodes having a memory and acting as a temporary master node for generating a second command message containing data stored in the memory thereof, or as a slave node for generating a response message in response to the first or second command message, said response message indicating particular information of the slave node, a method comprising the steps of:

• a) at said permanent master node, successively sending said first command message in a descending order of said priorities to each of the slave nodes, and updating the master memory with said response message returning from the slave node;
• b) at each one of said slave nodes, determining whether said first command message is received or not;
• c) if said first command message is determined to be received, updating the memory of the slave node with the data contained in the first command message, and returning said response message from the slave node to said permanent master node;
• d) if said first command message is determined to be not received, operating the slave node as said temporary master node by sending said second command message to a different one of other slave nodes;
• e) updating the memory of the temporary master node with said response message returning from said one slave node;
• and
• f) repeating the steps (d) and (e) until said second command message is received from a slave node whose priority is higher than the priority of the temporary master node.