5535212 : Implicit token media access protocol without collision detection

We claim:

• 1. A method for synchronizing a plurality of transceivers interconnected by a communications medium consisting of a single signal line, said plurality of transceivers being peers in that none is a predetermined central bus master, comprising:
  • assigning message transmission time slots uniquely to each of said transceivers;
  • when said communications medium is idle, providing a jam signal from one or more of said transceivers onto said communications medium, such that no message other than said jam signal may exist on said communications medium;
  • receiving said jam signal at said transceivers; and
  • transmitting, onto said communications medium, a communications medium ownership message from one of said transceivers that provided said jam signal, in a time slot associated with said one transceiver which is a first or subsequent time slot immediately following the end of said jam signal.
• 2. The method of claim 1, wherein said transceiver transmitting said communications medium ownership message is an initial token holder in an explicit token protocol.
• 3. A method for transmitting a message within a time slot uniquely associated with one transceiver of a plurality of transceivers interconnected by a communications medium consisting of a single signal line, said plurality of transceivers being peers in that none is a predetermined central bus master, comprising:
  • when said communications medium is idle, providing a jam signal from said one transceiver onto said communications medium such that no message other than said jam signal may exist on said medium;
  • receiving said jam signal at each of said plurality of transceivers;
  • transmitting said message from said one transceiver, onto said medium, in a time slot associated with said one transceiver which is a first or subsequent time slot immediately following the end of said jam signal; and
  • if there is a subsequent message which is to be transmitted by any of said plurality of transceivers, transmitting said subsequent message in a subsequent time slot associated with said any transceiver which is a first or subsequent time slot immediately following the end of said first message, but allowing said communications medium to become idle if no such subsequent message is available for transmission by said plurality of transceivers.
• 4. The method of claim 3, further comprising:
  • transmitting said subsequent message, wherein said subsequent message is a dummy message for merely preventing the bus from going idle, if no other messages are available for transmission.
• 5. A method for transmitting priority and nonpriority messages between a plurality of transceivers interconnected by a communications medium consisting of a single signal line, said plurality of transceivers being peers in that none is a predetermined central bus master, comprising:
  • when said communications medium is idle, providing a jam signal from one or more of said transceivers having a message to send onto said communications medium such that no message other than said jam signal may exist on said medium;
  • receiving said jam signal at each of said plurality of transceivers;
  • assigning fixed time slots to corresponding types of priority messages;
  • if there is a priority message to be transmitted by any of said transceivers, transmitting said priority message in a time slot assigned to said priority message which is a first or subsequent time slot immediately following the end of said jam signal; and
  • if there is a nonpriority message to be transmitted from one of said transceivers, transmitting said non-priority message in a time slot associated with said one of said transceivers which is a first or subsequent time slot immediately following the expiration of all of said fixed time slots and the end of transmission of said priority message, if any, or otherwise allowing said communications medium to become idle if no nonpriority message is available for transmission.
• 6. A method according to claim 5 wherein the association of each of said time slots rotates among all of said plurality of transceivers.
• 7. A method for transmitting priority and non-priority messages between a plurality of transceivers over a communications medium consisting of a single signal line, said plurality of transceivers being peers in that none is a predetermined central bus master, comprising:
  • when said communications medium is idle, providing a first jam signal from one of said transceivers having a message to send onto said communications medium such that no message other than said jam signal may exist on said medium;
  • assigning fixed time slots to corresponding ones of said transceivers;
  • if there is a priority message to be transmitted by any of said transceivers, transmitting said priority message in a time slot assigned to said one transceiver which is a first or subsequent time slot immediately following the end of said first jam signal;
  • if there is a nonpriority message to be transmitted by one of said transceivers, providing a second jam signal from said one transceiver onto said communications medium in a time slot associated with a group of transceivers which is less than all of said plurality of transceivers and of which said one transceiver is a member, which is a first or subsequent time slot immediately following the expiration of all of said fixed time slots and the end of transmission of said priority message, if any; and
  • transmitting said nonpriority message in a time slot associated with said one transceiver which is a first or subsequent time slot immediately following the end of said second jam signal.