Digital interface unit

• US 4,943,978 A
• Filed: 01/17/1989
• Issued: 07/24/1990
• Est. Priority Date: 11/27/1985
• Status: Expired due to Fees

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Rice, Thomas B.
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Edwards, Christopher O.
• Application Number:
  US07/298,293
• Time in Patent Office: 553 Days
• Field of Search: 370/43, 370/58, 370/60, 370/94.1, 370/99, 370/60.1, 370/94.2, 370/94.3, 375/1, 375/121, 178/2 B, 178/71 L
• US Class Current: 375/130
• CPC Class Codes: H04L 69/08 Protocols for interworking; Protocol conversion
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

An interface apparatus and method is disclosed which allows communication of digital data messages between a first type of data terminals (10 and 65) employing a message protocol (FIG. 1a) with a "free text-type" message, and other user devices employing other digital message protocols. The invention is adapted to exploit the free text message capability of the first protocol. In accordance with the invention, the incoming user data messages are packed into one or more free text messages of the first message protocol, and conversely "unpack" free text messages from the data terminal employing the first protocol are unpacked and formatted into the message protocol format employed by the user device 65. The invention eliminates the necessity for expensive translation devices which translate the data, and allows a plurality of user data terminals to communicate via a link comprising the data terminals employing the first message protocol.

Claims

1. Digital communication apparatus for use with a communications link, said communications link having a message protocol which includes a free text message protocol, said digital communications apparatus allowing transfer of data, over said communications link, between digital communications terminals of a predetermined type having a fixed format message protocol which is incompatible with the message protocol of said communications link, which comprises:

first means, adapted to receive a fixed format digital message having a fixed format message protocol from one of said digital communications terminals of said predetermined type, for packing said fixed format digital message into a free text digital message having a free text message protocol compatible with the free text message protocol of said communications link; and

second means, adapted to receive a free text digital message having a fixed format digital message contained therein from said communications link, for unpacking said fixed format digital message from said free text digital message, said second means being adapted to transmit said fixed format message to one of said digital communications terminals of said predetermined type.

2. The digital communication apparatus of claim 1 wherein said first means comprises:

means for storing said fixed format digital message received from one of said digital communications terminals;

means for identifying the message protocol type of said fixed format digital message;

means for tagging said fixed format digital message with digital identifiers indicating the fixed format message protocol type, that this message is to be transmitted as a free text message, and the terminal type to which said fixed format message is to be transmitted;

means for formatting said tagged fixed format digital message into said predetermined free text message format compatible with said communications link; and

means for storing said formatted free text message.

3. The digital communication apparatus of claim 2 wherein said means for formatting comprises:

means for creating a free text header word which includes said digital identifiers; and

means for copying said fixed format message into unoccupied digital words comprising said free text message.

4. The digital communication apparatus of claim 2 wherein said second means comprises:

means for storing a free text message received from said communications link;

means for detecting the receipt of said free text message from said communications link;

means for uniformatting said free text message to extract said fixed format message and identifiers therefrom;

means for reforming said fixed format message into the message protocol associated with the communications terminal identified in the transmitted message; and

means for transmitting said reformatted fixed format message to the identified digital communications terminal type.

5. The digital communication apparatus of claim 1 wherein said first and second means comprise:

storage buffer means for receiving and storing fixed format messages and free text messages; and

microprocessor means coupled to said storage buffer means for processing fixed format and free text messages stored therein, for identifying the message type of each fixed format digital message stored in said storage buffer means, for tagging each fixed format digital message with digital identifiers indicating the fixed format message protocol type, that this message is to be transmitted as a free text message, and the terminal type to which said fixed format message is to be transmitted, for formatting each tagged fixed format digital message into a predetermined free text message format compatible with said communications link, and for detecting the receipt of free text messages, for unformatting each free text message to extract the fixed format message therefrom by determining the fixed format message type, determining the terminal to which the fixed format message is to be sent, and unpacking the fixed format message from each free text message, and for storing each fixed format message in said storage buffer means prior to transmittal to the identified communication terminal.

15. The digital communications apparatus of claim 2 further comprising means for coupling a stored formatted free text message from said means for storing said formatted free text message to said communications link.

16. The digital communications apparatus of claim 15 wherein said means for formatting comprises:

means for creating a free text header word which includes said digital identifiers; and

means for copying said fixed format message into unoccupied digital words comprising said free text message.

6. Digital communication apparatus for use with secure, jam-resistant digital communication equipment, said digital communication equipment having a message protocol which includes a free text message protocol, said digital communication apparatus allowing transfer of data, over said digital communication equipment, between digital communications terminals of a predetermined type having a fixed format message protocol which is incompatible with the message protocol of said digital communication equipment, said digital communication apparatus comprising:

first means, adapted to receive fixed format digital messages having a fixed format message protocol compatible with said communications terminals, for packing said fixed format digital message into free text digital messages having a free text message protocol compatible with the free text message protocol of said jam-resistant digital communication equipment; and

second means adapted to receive free text digital messages compatible with said communication terminal and having a fixed format digital message contained therein, for unpacking said fixed format digital message from said free text digital message to provide said fixed format digital messages for use with said communication terminals.

7. The digital communication apparatus of claim 6 wherein said first means comprises:

means for storing said fixed format digital message received from said digital communications terminal;

means for identifying the message protocol type of said fixed format digital message;

means for tagging said fixed format digital message with digital identifiers indicating the fixed format message protocol type, that this message is to be transmitted as a free text message, and the terminal type to which said fixed format message is to be transmitted;

means for formatting said tagged fixed format digital message into said predetermined free text message format compatible with said communications link; and

means for storing said formatted free text message.

8. The digital communication apparatus of claim 7 wherein said means for formatting comprises:

means for creating a free text header word which includes said digital identifiers; and

means for copying said fixed format message into unoccupied digital words comprising said free text message.

9. The digital communication apparatus of claim 7 wherein said second means comprises:

means for storing a free text message received from said communications link;

means for detecting the receipt of said free text message from said communications link;

means for unformatting said free text message to extract said fixed format message and identifiers therefrom;

means for reformatting said fixed format message into the message protocol associated with the communications terminals identified in the transmitted message; and

means for transmitting said reformatted fixed format message to the identified digital communications terminal type.

17. The digital communications apparatus of claim 7 further comprising means for coupling a stored formatted free text message from said means for storing said formatted free text message to said communications link.

18. The digital communications apparatus of claim 17 wherein said means for formatting comprises:

means for creating a free text header word which includes said digital identifiers; and

means for copying said fixed format message into unoccupied digital words comprising said free text message.

10. A method of producing digital message compatible with a communications link derived from a digital communications terminal employing a message protocol incompatible with said communications link, said method comprising the steps of:

storing said fixed format digital message received from said digital communications terminal;

identifying the message protocol type of said fixed format digital message;

tagging said fixed format digital message with digital identifiers indicating the fixed format message protocol type, that this message is to be transmitted as a free text message, and the terminal type to which said fixed format message is to be transmitted;

formatting said tagged fixed format digital message into a predetermined free text message format compatible with said communications link; and

storing said formatted free text message.

11. The method of claim 10 wherein said step of formatting said free text message comprises the steps of:

creating a free text header word which includes said digital identifiers; and

copying said fixed format message into unoccupied digital word comprising said free text message.

12. A method of communicating between digital communications terminals employing a fixed message format and protocol using a communications link employing an incompatible message format and protocol, said method comprising the steps of:

storing a digital message having a predetermined fixed format derived from said digital communications terminal;

identifying the message type of said stored fixed format digital message;

tagging said fixed format digital message with digital identifiers indicating the fixed format message protocol type, that this message is to be transmitted as a free text message, and the terminal type to which said fixed format message is to be transmitted;

formatting said tagged fixed format digital message into a predetermined free text message format compatible with said communications link;

storing said formatted free text message;

transmitting said formatted free text message over said communications link;

storing a free text message received from said communications link;

detecting the receipt of said free text message from said communications link;

unformatting said free text message to extract said fixed format message and identifiers therefrom;

reformatting said fixed format message into the message protocol associated with the communications terminal identified in the transmitted free text message; and

transmitting said reformatted fixed format message to the identified digital communications terminal type.

13. The method of claim 12 wherein:

said step of formatting said free text message comprises the steps of creating a free text header word which includes said digital identifiers, and copying said fixed format message into unoccupied digital words comprising said free text message; and

said step of unformatting said free text message comprises the steps of determining the type of fixed format message contained in said free text message, and removing said fixed format message from the words of said free text message.

14. A method of communicating between digital communications terminals employing a fixed message format and protocol using a communications link employing an incompatible message format and protocol, said method comprising the steps of:

storing a digital message having a predetermined fixed format derived from said digital communications terminal;

identifying the message type of said stored fixed format digital message;

tagging said fixed format digital message with digital identifiers indicating the fixed format message protocol type, that this message is to be transmitted as a free text message, and the terminal type to which said fixed format message is to be transmitted;

formatting said tagged fixed format digital message into a predetermined free text message format compatible with said communications link;

storing said formatted free text message;

transmitting said formatted free text message over said communications link;

storing a free text message received from said communications link;

detecting the receipt of said free text message from said communications link;

unformatting said free text message to extract said fixed format message and identifiers therefrom;

unformatting said free text message to extract said fixed format message thereform, which includes determining the fixed format message type, determining the terminal to which the fixed format message is to be sent, and removing the fixed format message from said free text message; and

transmitting said reformatted fixed format message to the identified digital communications terminal type.