Apparatus for an improved ISDN terminal adapter having baud rate unblocking and methods for use therein

• US 6,031,848 A
• Filed: 05/07/1997
• Issued: 02/29/2000
• Est. Priority Date: 05/07/1997
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Brennan, Daniel M.
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): Pizarro, Ricardo
• Application Number:
  US08/852,658
• Time in Patent Office: 1,028 Days
• Field of Search: 375/219, 375/220, 375/221, 375/222, 370/522, 370/524, 370/523, 370/465, 370/466, 370/467, 370/241, 370/252
• US Class Current: 370/522
• CPC Class Codes: H04L 25/0262 Arrangements for detecting the data rate of an incoming signal
• CPC Class Codes: H04Q 11/0471 Terminal access circuits
• CPC Class Codes: H04Q 2213/13003 Constructional details of switching devices
• CPC Class Codes: H04Q 2213/13034 A/D conversion, code compression/expansion
• CPC Class Codes: H04Q 2213/1305 Software aspects
• CPC Class Codes: H04Q 2213/1307 Call setup
• CPC Class Codes: H04Q 2213/13093 Personal computer, PC
• CPC Class Codes: H04Q 2213/13097 Numbering, addressing
• CPC Class Codes: H04Q 2213/13103 Memory
• CPC Class Codes: H04Q 2213/13106 Microprocessor, CPU
• CPC Class Codes: H04Q 2213/13109 Initializing, personal profile
• CPC Class Codes: H04Q 2213/1316 Service observation, testing
• CPC Class Codes: H04Q 2213/13166 Fault prevention
• CPC Class Codes: H04Q 2213/13174 Data transmission, file transfer
• CPC Class Codes: H04Q 2213/13175 Graphical user interface [GUI], WWW interface, visual indication
• CPC Class Codes: H04Q 2213/13176 Common channel signaling, CCS7
• CPC Class Codes: H04Q 2213/13199 Modem, modulation
• CPC Class Codes: H04Q 2213/13202 Network termination [NT]
• CPC Class Codes: H04Q 2213/13204 Protocols
• CPC Class Codes: H04Q 2213/13209 ISDN
• CPC Class Codes: H04Q 2213/13213 : Counting, timing circuits
• CPC Class Codes: H04Q 2213/13216 : Code signals, frame structure
• CPC Class Codes: H04Q 2213/13297 : Coupling different rates in TDM systems, data rate adaptation
• CPC Class Codes: H04Q 2213/13298 : Local loop systems, access network
• CPC Class Codes: H04Q 2213/13299 : Bus
• CPC Class Codes: H04Q 2213/13362 : Asynchronous systems
• CPC Class Codes: H04Q 2213/13389 : LAN, internet
• CPC Class Codes: H04Q 2213/13405 : Dual frequency signaling, DTMF

Abstract

Apparatus for an improved ISDN terminal adapter (5) and accompanying methods for use therein. The adapter provides automatic ISDN switch detection, automatic SPID configuration, baud rate unblocking and automatic data compression. Specifically, with respect to baud rate unblocking, the adapter detects instances of baud rate blocking, through excessive communication errors for a known input, and forces the adapter to relinquish its high speed setting and automatically return to autobaud operation but at a lower maximum speed.

Claims

1. A method for preventing baud rate blockage from occurring between first and second communicating devices, said first and second devices communicating with each other via a serial connection extending therebetween, the first and second devices being data circuit terminating equipment (DCE) and data terminal equipment (DTE), respectively, the DCE being capable of establishing communication through a communication link, separate from the serial connection, with a DCE peer device, wherein the DCE provides either said fixed baud rate operation or autobaud operation and the DTE provides fixed baud rate operation, the method comprising the steps of, in the DCE:

detecting whether the DCE is set to said fixed baud rate operation;

if the DCE is set to said fixed baud rate operation, providing an indication signifying said fixed baud rate operation so as to obtain, via the serial connection, entries from the DTE of at least one pre-defined data value occurring over a pre-defined interval of time;

obtaining said entries, in response to the indication, from the DTE and communicated over the serial connection;

detecting, in response to said entries communicated by the DTE to the DCE, communication errors arising from a baud rate mismatch between the DCE and the DTE; and

in the event a totalized number of said communication errors occurring during said interval exceeds a predefined threshold, changing operation of the DCE from the fixed baud rate operation to the autobaud operation whereby the DCE can detect a fixed baud rate then being used by the DTE for communication over the serial connection and set its own baud rate for communication over said connection to match that of the DTE so as to prevent said baud rate blockage from occurring between the DTE and DCE for communication over the serial connection therebetween.

3. The method in claim 1 wherein the indication providing step comprises the step of providing a predefined visual indication at the DCE.

4. The method in claim 3 wherein the method further comprises the steps, occurring at the DTE, of:

repetitively depressing, in response to the indication, a key on a keyboard associated with the DTE during the predefined interval of time so as to generate, within the DTE, a stream of identical predefined serial data values as said entries; and

transmitting said entries over the serial connection to the DCE.

5. The method in claim 4 wherein the DCE comprises a terminal adapter or a modem.

6. The method in claim 5 wherein the predefined data value is an ASCII pattern associated with said key.

7. The method in claim 6 wherein the predefined interval is at least five seconds and the predefined threshold is at least five.

8. The method in claim 7 wherein the key is the letter "A" and the predefined data value is the hex value 41.

9. The method in claim 5 wherein the DTE comprises a computer.

10. The method in claim 9 wherein the predefined data value is an ASCII pattern associated with said key.

11. The method in claim 10 wherein the predefined interval is at least five seconds and the predefined threshold is at least five.

12. The method in claim 11 wherein the key is the letter "A" and the predefined data value is the hex value 41.

2. Apparatus for preventing baud rate blockage from occurring between first and second communicating devices, said first and second devices communicating with each other via a serial connection extending therebetween, the first and second devices being data circuit terminating equipment (DCE) and data terminal equipment (DTE), respectively, the DCE being capable of establishing communication through a communication link, separate from the serial connection, with a DCE peer device, wherein the DCE provides either said fixed baud rate operation or autobaud operation and the DTE provides fixed baud rate operation, the apparatus comprising, in the DCE:

a first processor;

a first memory for storing first executable instructions therein; and

serial communications circuitry, connected to the processor, for interfacing to said serial connection; and

wherein the processor, in response to the stored first instructions;

detects whether the DCE is set to said fixed baud rate operation;

if the DCE is set to said fixed baud rate operation, provides an indication signifying said fixed baud rate operation so as to obtain, via the serial connection, entries from the DTE of at least one pre-defined data value occurring over a pre-defined interval of time;

obtains said entries, in response to the indication, from the DTE and communicated over the serial connection;

detects, in response to said entries communicated by the DTE to the DCE, communication errors arising from a baud rate mismatch between the DCE and the DTE; and

in the event a totalized number of said communication errors occurring during said interval exceeds a predefined threshold, changes operation of the DCE from the fixed baud rate operation to the autobaud operation whereby the DCE can detect a fixed baud rate then being used by the DTE for communication over the serial connection and set its own baud rate for communication over said connection to match that of the DTE so as to prevent said baud rate blockage from occurring between the DTE and DCE for communication over the serial connection therebetween.

13. The apparatus in claim 2 wherein the first processor, in response to the first executable instructions and if the DCE is set to the fixed baud rate operation, provides a predefined visual indication thereof at the DCE.

14. The apparatus in claim 13 wherein the DTE comprises a second processor, a second memory for storing second executable instructions therein, and a keyboard, and the second processor, in response to the second executable instructions stored in the second memory:

generates a stream of identical predefined serial data values as said entries in response to repetitive user depressions of a key on the keyboard during the predefined interval of time; and

transmits said entries over the serial connection to the DTE.

15. The apparatus in claim 14 wherein the DCE comprises a terminal adapter or a modem.

16. The apparatus in claim 15 wherein the DCE comprises an ISDN terminal adapter having:

first and second independent B-channel hardware data link controller (HDLCs);

an ISDN line interface for interfacing two separate corresponding B channels in a 2B+D ISDN line to said first and second B-channel controllers, and, D-channel signaling, to the processor; and

connections, established by the first processor through execution of said first executable instructions, between an individual one of said B-channel HDLCs and either said first or second B-channels in said ISDN line.

17. The apparatus in claim 15 wherein the predefined data value is an ASCII pattern associated with said key.

18. The apparatus in claim 17 wherein the predefined interval is at least five seconds and the predefined threshold is at least five.

19. The apparatus in claim 18 wherein the DCE comprises an ISDN terminal adapter having:

first and second independent B-channel hardware data link controllers (HDLCs);

an ISDN line interface for interfacing two separate corresponding B channels in a 2B+D ISDN line to said first and second B-channel controllers, and, D-channel signaling, to the processor; and

connections, established by the first processor through execution of said first executable instructions, between an individual one of said B-channel HDLCs and either said first or second B-channels in said ISDN line.

20. The apparatus in claim 19 wherein the key is the letter "A" and the predefined data value is the hex value 41.

21. The apparatus in claim 15 wherein the DTE comprises a computer.

22. The apparatus in claim 21 wherein the predefined data value is an ASCII pattern associated with said key.

23. The apparatus in claim 22 wherein the predefined interval is at least five seconds and the predefined threshold is at least five.

24. The apparatus in claim 23 wherein the DCE comprises an ISDN terminal adapter having:

first and second independent B-channel hardware data link controllers (HDLCs);

an ISDN line interface for interfacing two separate corresponding B channels in a 2B+D ISDN line to said first and second B-channel controllers, and, D-channel signaling, to the processor; and

connections, established by the first processor through execution of said first executable instructions, between an individual one of said B-channel HDLCs and either said first or second B-channels in said ISDN line.

25. The apparatus in claim 24 wherein the key is the letter "A" and the predefined data value is the hex value 41.