Contention free local area network

• US 5,422,885 A
• Filed: 06/01/1992
• Issued: 06/06/1995
• Est. Priority Date: 06/01/1992
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Nadkarni, Vijay J.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US07/891,012
• Time in Patent Office: 1,100 Days
• Field of Search: 370/85.1, 370/85.2, 370/85.3, 370/85.4, 370/85.5, 370/85.9, 370/85.11, 370/85.12, 370/85.14, 370/85.15, 370/110.1, 370/67, 370/95.1, 370/95.3, 370/97 , 370/16.1, 340/825.02, 340/825.05, 340/825.07, 340/825.08, 340/825.5, 455/14, 455/16, 455/17, 455/51.1, 455/56.1
• US Class Current: 370/451
• CPC Class Codes: H04L 12/417 with deterministic access, e.g. token passing

Abstract

A contention free local area network includes a token passing control bus (102) and a data bus (104) coupled to a plurality of communication nodes ( 108, 112, 114, 116, 118, and 120). The control bus (102) allows for a transmit-enable token to be daisy-chained along the plurality of communication nodes. When one of the communication nodes wants to transmit a message, the node upon receiving the transmit-enable token holds the token until it transmits its message along a data bus (104) to the other communication nodes. Once the message is transmitted, the particular communication node releases the transmit-enable token, allowing the token to continue to be rotated among the plurality of communication nodes (108, 112, 114, 116, 118 and 120).

Claims

1. A method of transmitting a message in a communication network having a plurality of communication nodes, the communication network including a multi-drop data bus interconnecting said plurality of communication nodes for allowing messages to be transmitted among said plurality of communication nodes, and a control bus comprising inbound and outbound token passing links coupled to each of said plurality of communication nodes in a daisy-chain arrangement which allows for a transmit-enable token to be passed along said plurality of communication nodes, the method of transmitting a message by a select one of said plurality of communication nodes comprising the steps of:

determining if the transmit-enable token has been received at the inbound token link that is coupled to said select one communication node which is requesting to transmit the message;

transmitting the message via said multi-drop data bus to each of said plurality of communication nodes, once the transmit-enable token has been received; and

sending the transmit-enable token to the next communication node in the control bus daisy-chain arrangement via the outbound token passing link that is coupled to the communication node which has transmitted the message once the message is transmitted.

2. A method of transmitting a message by a communication node in a communication network as defined in claim 1, further comprising the step of:

randomly enabling a request-to-transmit signal when said select one communication node wants to transmit the message, the request-to-transmit signal causes said select one communication node to retain control of the transmit-enable token until the message has been transmitted.

3. A method of transmitting a message by a communication node in a communication network as defined in claim 2, wherein the step of determining that the transmit-enable token has been received comprises determining if a voltage level on the inbound token passing link has changed from a first voltage state to a second voltage state.

4. A method of transmitting a message in a communication network having a plurality of communication nodes, the communication network including a multi-drop data bus interconnecting said plurality of communication nodes for allowing messages to be transmitted among said plurality of radio frequency repeaters, and a control bus comprising inbound and outbound token passing links coupled to each of said plurality of communication nodes in a daisy-chain arrangement which allows for a transmit-enable token to be passed along said plurality of communication nodes, the method of transmitting a message comprising the steps of:

enabling a request-to-send signal at a select one of said plurality of communication nodes which is requesting to transmit a message;

determining if the transmit-enable token has been received via the inbound token passing link which is coupled to the said select one communication node;

transmitting the message via the multi-drop data bus to each of said plurality of communication nodes, if the transmit enable token has been received;

disabling the request-to-send signal upon having completed transmission of the message; and

sending the transmit-enable token via the outbound token passing link which is coupled to the said select one communication node.

5. A method of transmitting a message in a communication network as defined in claim 4, wherein the step of enabling the request-to-send signal is done randomly in time.

6. A method of transmitting a message in a communication network as defined in claim 4, wherein the step of determining if the transmit-enable token has been received comprises determining if a voltage level in the inbound token passing link of the communication node requesting to transmit the message has changed from a first voltage state to a second voltage state.

7. A method of transmitting a message in a communication network as defined in claim 6, comprising the further step of:

maintaining possession of the transmit-enable token until the message has been transmitted by maintaining a voltage level present at an outbound token passing link which is coupled to the communication node transmitting the message at a first voltage state while the message is being transmitted.

8. A method of transmitting a message in a communication network as defined in claim 7, wherein the step of sending the transmit-enable token via the outbound token passing link to the next communication node in the control bus daisy-chain arrangement comprises changing the voltage level in the outbound token passing link from the first voltage state back to the second voltage state.

9. A communication system, comprising:

a plurality of radio frequency repeaters for relaying radio frequency information signals;

a multi-drop data bus interconnecting said plurality of radio frequency repeaters for allowing messages to be transmitted among said plurality of radio frequency repeaters; and

a control bus coupled in a daisy-chain arrangement to said plurality of radio frequency repeaters for allowing a token to be passed among said plurality of radio frequency repeaters, said plurality of radio frequency repeaters each including a control means responsive to the reception of the token for allowing a radio frequency repeater from among said plurality of radio frequency repeaters which has received the token and is requesting to transmit a message via said multi-drop data bus.

10. A communication system as defined in claim 9, wherein if one or more, but not all, of the radio frequency repeaters becomes inoperative, the data bus will continue to allow messages to be transmitted among said radio frequency repeaters that are still operative and the control bus will continue to allow the token to be passed among said radio frequency repeaters which are still operative.

11. A communication system as defined in claim 9, wherein the control bus comprises a set of inbound and outbound token passing links coupled to each of said radio frequency repeaters and the control means determines if a token has been received at a particular radio frequency repeater from among the plurality of radio frequency repeaters by determining if a voltage level present at the inbound token passing link of the particular repeater has changed from a first voltage level to a second voltage level.