TERMINAL INTERFACE FOR A SERIAL LOOP COMMUNICATIONS SYSTEM HAVING STORE AND FORWARD CAPABILITY

• US 3,781,815 A
• Filed: 02/15/1972
• Issued: 12/25/1973
• Est. Priority Date: 02/15/1972
• Status: Expired due to Term

• Current Assignee: Eual A. Moss, Paul E. Boudreau, Robert A. Donnan, Roy C. Dixon
• Original Assignee: Eual A. Moss, Paul E. Boudreau, Robert A. Donnan, Roy C. Dixon
• Inventors: Boudreau, Paul E., Dixon, Roy C., Donnan, Robert A., Moss, Eual A.
• Primary Examiner(s): Henon, Paul J.
• Assistant Examiner(s): Vandenburg, John P.
• Application Number:
  US05/226,443
• Time in Patent Office: 679 Days
• Field of Search: 340/172.5
• US Class Current: 709/234
• CPC Class Codes: G06F 13/4213 with asynchronous protocol
• CPC Class Codes: H04L 12/433 with asynchronous transmission, e.g. token ring, register insertion

Abstract

A serial loop data communications system having store and forward capability at each terminal interface on the loop and in which data signal entities, each of which includes a plurality of data bits, addressed to subsequent terminals on the loop are stored in successive locations in a serial storage device when received if a terminal associated with the interface is transmitting. At the termination of data transmission by the associated terminal, the previously stored data signal entities are forwarded from the data entity storage position occupied by the oldest received entity and subsequently received entities are advanced to successive entity storage positions until data signal entities for subsequent terminals on the loop are no longer received, at which time advancement of the data signal entities is terminated and the data signal entities then remaining in storage, are forwarded from the successive entity storage locations in the serial storage in the order of receipt.

Claims

1. A store and forward interface for a serial loop data communications system comprising:

a first data path for bypassing multibit data entity signals on the loop around the interface;

first control means for selectively enabling and disabling said first data path;

a second data path for accepting data from said loop and reinserting the data accepted at a later time, said second path including;

storage means having a plurality of sequentially arranged multibit data entity storage locations, a local source of multibit data entity signals, means for selectively connecting the storage means and the local source to the communications loop, and second control means responsive to said local source of data entity signals and said data entity signals on the loop for providing;

first signals indicative of the status of the storage means for controlling said storage means;

second signals to said first control means for interrupting said bypass data signal path and for connecting said local data entity source to the loop for transmitting data entity signals when said storage device status signals indicate that the storage means has no data entity signals stored therein, the local source has data entity signals to transmiT, and data entity signals for subsequent interfaces are not being received;

third signals for controlling said storage means to cause data signal entities received while the local source is transmitting data entity signals to be stored in successive entity storage locations under control of said first signals; and

fourth signals when said first signals indicate that the storage contains data entity signals and said local source completes transmission for connecting said storage means to the loop to transmit the stored signal entities to the loop in the order received;

said second control means inhibiting changes in the first signals indicating the storage status when the third and fourth signals occur simultaneously whereby received data entity signals are inserted as received in the same storage location and transmitted data entity signals are removed from the same storage location.

2. A store and forward interface for a serial loop data communications system as set forth in claim 1, in which said storage means having a plurality of sequentially arranged multibit data entity storage locations includes:

a serial shift register divided into a plurality of multibit sections each capable of storing a single multibit data entity;

first means responsive to said third signals for applying said received data entity signals to the first section of the serial shift register;

second means responsive to said third signals for applying shifting pulses to all of the shift register sections whereby the bits comprising the data signals are inserted into the shift register in the order received;

third means responsive to said fourth signals and said first signal for applying shifting pulses to the shift register sections indicated by the said first signal whereby the data entity stored in the indicated sections is shifted; and

fourth means responsive to said first and fourth signals for connecting the indicated section to the means for selectively connecting the storage means to the communications loop.

3. A store and forward interface for a serial loop data communications system as set forth in claim 2, in which said second control means includes;

a bidirectional counter having incrementing and decrementing inputs and a plurality of unique outputs at least one greater in number than the number of stages in the serial shift register;

first means for applying signals to said counter incrementing input each time a data entity is received for storage in the register;

second means for applying signals to said counter decrementing input each time a data entity is to be transmitted from the storage; and

third means for inhibiting changes in the counter when data entities are to be simultaneously received for storage and transmitted from storage.

4. A store and forward interface for a serial loop data communications system as set forth in claim 1, in which said storage means having a plurality of sequentially arranged multibit data entity storage locations includes:

a serial shift register divided into a plurality of multibit sections each capable of storing a single multibit data entity;

first means responsive to said third signals and said first signals for applying said received data entity signals to the shift register section indicated by the first signals;

second means responsive to the third signals and the first signals for applying shifting pulses to the section of the shift register indicated by the first signals whereby the bits comprising each data entity are inserted into the sections indicated by the first signals;

third means responsive to said fourth signals for applying shifting pulses to all of the shift register sections whereby the stored bits are shifted towards the final section; and

fourth means responsive to said fourth signals for connecting the final section of the shift register to the means for selectively connecting the storage means to the communications loop whereby data entitiEs are transmitted under control of said fourth signals in the order received.

5. A store and forward interface for a serial loop data communications system as set forth in claim 4, in which said second control means includes:

a bidirectional counter having incrementing and decrementing inputs and a plurality of unique outputs at least one greater in number than the number of stages in the serial shift register;

first means for applying signals to said counter incrementing input each time a data entity is received for storage in the register;

second means for applying signals to said counter decrementing input each time a data entity is to be transmitted from the storage; and

third means for inhibiting changes in the counter when data entities are to be simultaneously received from storage and transmitted from storage.