ISDN interface unit

• US 5,764,643 A
• Filed: 01/31/1997
• Issued: 06/09/1998
• Est. Priority Date: 11/29/1990
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Okuyama, Satoshi, Matsukura, Ryuichi, Takebayashi, Tomoyoshi, Hasegawa, Hiroki, Azami, Toshihiro
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US08/791,331
• Time in Patent Office: 494 Days
• Field of Search: 370/466, 370/467, 370/522, 370/524, 370/545, 370/904, 370/433, 370/463, 341/75, 375/216
• US Class Current: 370/463
• CPC Class Codes: H04Q 11/0471 Terminal access circuits
• CPC Class Codes: H04Q 2213/13031 Pulse code modulation, PCM
• CPC Class Codes: H04Q 2213/13034 A/D conversion, code compression/expansion
• CPC Class Codes: H04Q 2213/1309 Apparatus individually associated with a subscriber line, line circuits
• CPC Class Codes: H04Q 2213/13093 Personal computer, PC
• CPC Class Codes: H04Q 2213/13103 Memory
• CPC Class Codes: H04Q 2213/13106 Microprocessor, CPU
• CPC Class Codes: H04Q 2213/13174 Data transmission, file transfer
• 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 2213/13209 ISDN
• CPC Class Codes: H04Q 2213/13214 Clock signals
• CPC Class Codes: H04Q 2213/1327 Release and resetting of connection
• CPC Class Codes: H04Q 2213/13271 Forced release
• CPC Class Codes: H04Q 2213/13292 Time division multiplexing, TDM
• CPC Class Codes: H04Q 2213/13297 Coupling different rates in TDM systems, data rate adaptation
• CPC Class Codes: H04Q 2213/13299 Bus
• CPC Class Codes: H04Q 2213/1332 Logic circuits
• CPC Class Codes: H04Q 2213/13322 Integrated circuits
• CPC Class Codes: H04Q 2213/1336 : Synchronisation
• CPC Class Codes: Y10S 370/904 : Integrated Services Digital Network, ISDN

Abstract

An ISDN interface unit interconnects a data processing unit, an ISDN, and an analog telephone and comprises a DMA request signal generation circuit for generating a DMA request signal from an 8 kHz clock signal from an ISDN line. In accordance with the request signal, PCM coded data input from the ISDN line is transferred, using DMA, to a memory of the data processing unit or vice versa, or the ISDN interface unit comprises a code conversion circuit, data stored in the data processing unit are converted to nonlinear PCM coded data and transmitted to the ISDN line or vice versa. Further, the ISDN interface unit comprises communication functions for the digital signal and for the voice band signal, a control channel signal sent from the ISDN line is interpreted, and one of the communication functions can be selected.

Claims

1. An ISDN interface unit coupled between a data processing unit and an ISDN line, comprising:

a digital signal communication circuit; and

a voice band signal communication circuit;

one of said digital signal and voice band signal communication circuits being selected by said ISDN interface unit based on a control channel signal on the ISDN line, so that transmission is initially carried out on the ISDN line in a form to match the digital signal communication circuit, and

when a response from a communication partner is received, communication is carried out by using the digital signal communication circuit; and

when a disconnect message is received instead of the response, a retransmission is automatically carried out to match the voice band signal communication circuit.

2. An ISDN interface unit as set forth in claim 1, wherein:

said digital signal communication circuit comprises at least a data link control circuit and a rate adaptation circuit, and

said voice band signal communication circuit comprises at least a modem circuit and a voice codec.

3. An ISDN interface unit as set forth in claim 2 further comprising:

an ISDN connection circuit for executing a physical interface in connection with the ISDN line, for separating a digital signal when the digital signal from the ISDN line is received, and for obtaining a control channel signal for connection to the ISDN;

a personal computer interface circuit for interfacing between the data processing unit and the ISDN interface unit;

a buffer circuit for data transmitted to the ISDN line and supplied from the ISDN line, and

a telephone interface circuit for interfacing to a connected analog telephone.

4. A method for processing communications between the data processing unit and an ISDN line, comprising:

selecting one of a digital signal communications circuit and a voice band communication circuit based on a control channel signal on the ISDN line;

initially carrying out transmission on the ISDN line in a form to match the digital signal communication circuit;

carrying out communication on the ISDN line using the digital signal communication circuit when a response from a communication partner is received;

if a disconnect message is received instead of a response, automatically carrying out retransmission to match the voice band signal communication circuit.