Power-saving full duplex nodal communications systems

• US 5,359,594 A
• Filed: 05/15/1992
• Issued: 10/25/1994
• Est. Priority Date: 05/15/1992
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lackritz, Neal M., Gould, Joel M.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Nguyen, Chau T.
• Application Number:
  US07/884,538
• Time in Patent Office: 893 Days
• Field of Search: 370/32.1, 370/24, 370/29, 370/100.1, 370/49, 370/17, 370/13, 370/16, 370/103, 340/825.2, 340/825.14, 340/825.21, 340/870.39, 455/88, 455/116, 455/343, 455/70
• US Class Current: 370/276
• CPC Class Codes: G06F 1/3215 Monitoring of peripheral devices
• CPC Class Codes: H04L 1/24 Testing correct operation
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04L 5/1461 Suppression of signals in the return path, i.e. bidirectional control circuits
• CPC Class Codes: H04L 69/28 Timers or timing mechanisms used in protocols
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

An inter-nodal communication system employs full duplex transmission links to connect asynchronously operating nodes. Links between nodes are quiesced to a no-current flow state in the absence of message traffic. The system employs a communication protocol that incorporates time-outs which (1) enable a broken link to be detected at the inception of a message and (2) prevent a receiver from listening to a link which has been quiesced by a transmitter at the other end of a link that is shutting-off. All synchronization messages in the inter-nodal communication network are carried by data links and no additional communication wires are required.

Claims

1. A system for enabling communications coordination between first and second nodes, said nodes operating asynchronously and having a full duplex transmission link connected therebetween, each node having transmitting means and receiving means connected by lines of said full duplex transmission link for forward and reverse direction message handling, a receiver means at said first node and a transmitter means at said second node connected via a line termed "mates" and a receiver means and a transmitter means resident in a single node and connected to said full duplex transmission link termed "partners", the system comprising:

means coupled to said transmission link for quiescing a line between mates to a non-current flow state in the absence of message traffic;

means responsive to message traffic for enabling lines comprising said full duplex transmission link whenever a message is to be transmitted, by causing said transmitter means at said first node to transmit to said receiver means at said second node, at least a synch character at both a start and an end of a message, said transmitter means at said first node continuing for a period after a synch character at the end of said message to generate blank signals; and

stopping means at said second node responsive to said synch character at the end of said message received from said transmitter means at said first node for controlling said receiver means at said second node to cease detecting signals after a pending time out which commences substantially upon receipt of said synch character, said pending time out set to expire before said transmitter means at said first node ceases transmission of said blank signals.

2. The system as recited in claim 1 further comprising:

means responsive to said received synch character at the end of said message for enabling said receiver means at said second node to enter a quiescent state after receipt of said synch character at the end of said message from said transmitter means at said first node and before said pending time out expires, unless data is received from said transmitter means at said first node within said pending time out.

3. The system as recited in claim 1, further comprising:

means responsive to a message start to cause synch characters to be transmitted by transmitter means in said first and second nodes in both forward and reverse directions over lines comprising said full duplex transmission link to test for broken lines in said full duplex transmission link.

4. A method for enabling communications coordination between first and second nodes, said nodes operating asynchronously and having a full duplex transmission link connected therebetween, each node having transmitting means and receiving means connected to said full duplex transmission link for forward and reverse direction message handling, receiver means and transmitter means connected over a line of said link termed "mates" and receiver means and transmitter means resident in a single node and connected to said full duplex transmission link termed "partners", the method comprising the steps of:

a. quiescing a line between mates to a non-current flow state in the absence of message traffic;

b. enabling a transmitter means at said first node to activate its connected line and to transmit to a receiver means mate at said second node, synch characters at both a start and end of a message;

c. activating in said first node, a Starting timeout when said transmitter means at said first node commences Running and transmits a synch character; and

d. operating said receiver means mate in said second node to respond to data following a received synch character from said transmitter means in said first node, by entering a Running state, entry into said Running state causing a transmitter means partner in said second node to activate its connected line and to transmit a synch character to a receiver means mate in said first node, continuity of said full duplex transmission link in forward and reverse directions being assured by receipt of a synch character by said receiver means mate in said first node prior to the expiry of said Starting timeout.

5. The method as recited in claim 4 wherein said receiving means mate in said second node responds to a synch character at the end of a message by entering a Pending state wherein a Pending timeout is commenced, said method comprising the further step of:

causing said transmitter means in said first node to enter a Stopping state subsequent to transmission of the synch character at the end of the message, said Stopping state causing commencement of a Stopping timeout which is longer in duration than said Pending timeout, said receiver means mate at said second node, at the expiry of said Pending timeout, entering a quiescent state and said transmitter means at said first node entering a quiescent state subsequent thereto due to the longer duration of said Stopping timeout.

6. The method as recited in claim 5 wherein said transmitter means in said first node, upon entering said Stopping state, sends blank signals to its receiving means mate, said receiving means mate receiving said blank signals and terminating its reception while said blank signals are continuing to be transmitted due to expiry of said Pending timeout prior to expiry of said Stopping timeout.

7. The method as recited in claim 6 wherein the duration of said Stopping timeout is greater than or equal to the time required for a round trip of a signal over lines connecting said first and second nodes plus the maximum amount of time a receiver means mate to said transmitter means in said first node can spend in the Pending state.

8. A method for enabling communications coordination between first and second nodes that operate asynchronously and have a full duplex transmission link connecting them, each node having transmitting and receiving means for forward and reverse direction message handling, a receiver means and a transmitter means connected between nodes via a line termed "mates" and a receiver means and a transmitter means resident in a single node termed "partners" each transmitter means transmitting a synch character at both ends of a message, the method comprising the steps of:

enabling a transmitter means in said first node to transmit a synch character to a receiver means mate in said second node, said transmitter means in said first node then entering a Stopping state and subsequently transmitting blanks during a Stopping timeout; and

causing said receiver means in said second node to respond to said synch character from said transmitter means in said first node, when a transmitting means partner of said receiver means at said second node is not in a Running state, by switching to a Pending state to commence a Pending timeout and to subsequently switch to a Quiet state wherein all signals are ignored except for a synch character, said receiver means in said second node switching to said Quiet state only if a message is not received prior to said Pending timeout, said Pending timeout exhibiting a lesser duration than said Stopping timeout.

9. The method as recited in claim 8 wherein said receiver means in said second node responds to said transmitter means partner entry into a Running state during said Pending timeout and prior to receipt of a message, by entering an Idle state to await receipt of further signals from its transmitter means mate.

10. The method as recited in claim 9 wherein said receiver means mate in said second node responds to a second received synch character prior to said Pending timeout to reset said pending timeout and cause it to restart.

11. The method as recited in claim 10 wherein said receiver means in said second node responds to a message received prior to said Pending timeout, by causing said transmitter means partner to enter a Running state and to transmit a synch character to a receiver means mate in said first node.

12. A method for enabling communications coordination between first and second nodes that operate asynchronously and have a full duplex transmission link connecting them, each node having transmitting and receiving means for forward and reverse direction message handling, respectively, a receiver means and a transmitter means connected between nodes via a line termed "mates" and a receiver means and a transmitter means resident in a single node termed "partners" each transmitter means transmitting a synch character at both ends of a message, the method comprising the steps of:

enabling a transmitter means in a first node to transmit a synch character to a receiver means mate in a second node, said transmitter means in said first node then entering a Stopping state and subsequently transmitting blanks during a Stopping timeout;

causing said receiver means mate in said second node to respond to said transmitted synch character when its transmitting means partner is in a Running state, by switching to an Idle operational state until said Running state terminates or until a message is received, whichever occurs first;

enabling said receiver means mate in said second node to respond to a message if said synch character precedes said message or to respond to a control signal that occurs as a result of the operation of said transmitter means partner, said receiver means mate in said second node further responding to its transmitter means partner'"'"'s entry into a non-Running state by entering a Pending state and commencing a Pending timeout.