Dual master implied token communication system
AssigneeRosemount Inc.
InventorJogesh Warrior
Life of this patent
Estimating the term…
Abstract
A pair of master units share a common communication link to communicate with one or more slave units. Each slave unit transmits a message only in response to a message from one of the master units. When an initial transmission request is received by a master unit, it monitors the communication link and only initiates transmission of a message when the link has been quiet for a link quiet time period. After completing a transmission of a message, the master unit waits a link grant time period before transmitting again to permit the other master unit an opportunity to transmit a message if it desires. Synchronization of the two master units, therefore, is achieved quickly and with minimum overhead.
Claims7
A method in a communication system in which only first and second master units send messages to and receive messages from at least one slave unit having a unique slave unit address over a common communications link, comprising:
- for the first master unit:
- sending an initial message comprising the steps of:
- waiting for a clear channel on the communication link;
- setting a link quiet timer;
- enabling transmission of the initial message to the slave unit if a message from the slave unit to the second master unit is detected on the communication link;
- enabling transmission of the initial message if the link quiet timer times out and no transmissions have been detected on the communication link;
- and
- setting a link grant timer;
- sending subsequent messages comprising the steps of:
- enabling transmission of a subsequent message to the slave unit if the link grant timer times out and no messages from the second master unit have been detected on the communication link;
- setting the link quiet timer if a message from the second master unit is detected on the communication link and:
- enabling transmission of the subsequent message if a message from the slave unit to the second master unit is detected on the communication link;
- enabling transmission of the subsequent message if the link quiet timer times out and no messages have been detected on the communication link;
- setting the quiet timer and repeating the steps of sending subsequent messages;
- whereby as long as the second master unit does not transmit on the communication link, the first master nit transmits subsequent messages with only a delay of waiting for the link grant timer to time out;
- for the second master;
- sending an initial message comprising the steps of:
- waiting for a clear channel on the communication link;
- setting a link quiet timer;
- enabling transmission of the initial message to the slave unit if a message from the slave unit to the first master unit is detected on the communication link;
- enabling transmission of the initial message if the link quiet timer times out and no transmissions have been detected on the communication link;
- and setting a link grant timer;
- sending subsequent messages comprising the steps of:
- enabling transmission of a subsequent message to the slave unit if the link grant timer times out and no messages from the first master unit have been detected on the communication link;
- setting the link quiet timer if a message from the first master unit is detected on the communication link and:
- enabling transmission of the subsequent message if a message from the slave unit to the first master unit is detected on the communication link;
- enabling transmission of the subsequent message if the link quiet timer times out and no messages have been detected on the communication link;
- setting the quiet timer and repeating the steps of sending subsequent messages;
- whereby as long as the first master unit does not transmit on the communication link, the second master unit transmits subsequent messages with only a delay of waiting for the link grant timer to time out.
Dependencies are inferred from the claim text.