United States Patent [19]
`Mills
`
`[54] COMBINED ANALOG AND DIGITAL
`COMMUNICATIONS DEVICE
`
`[75] Inventor: Andrew Mills, Austin, Tex.
`[73] Assignee: Advanced Micro Devices, Inc.,
`Sunnyvale, Calif.
`
`US0058.15505A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,815,505
`Sep. 29, 1998
`
`[57]
`
`ABSTRACT
`
`A communications device is presented which is configured
`to provide selective signal processing at a “plain old tele
`phone service” (POTS) interface, an ISDN U interface, or an
`ISDN S/T interface. A first POTS connector allows the
`communications device to be connected to an analog POTS
`telephone line. A second ISDN U connector allows the
`[21] Appl. No.: 696,201
`communications device to be connected to an ISDN network
`[22] Filed:
`Aug. 13, 1996
`at an ISDN U interface point. A third ISDN S/T connector
`[51] Int. Cl." … H04Q 11/00
`allows the communications device to be connected to an
`ISDN network at an ISDN S/T interface point. A digital
`[52] U.S. Cl. .......................... 370/522; 370/264; 370/463;
`signal processing (DSP) core performs: (i) analog modem
`379/.399
`[58] Field of Search ..................................... 370/420, 522,
`functions via analog modem emulation when a POTS tele
`370/524, 465, 463, 264; 375/219, 220;
`phone line is connected to the POTS connector, or (ii) ISDN
`379/.399
`digital voice and data processing functions along with ISDN
`S/T and U interface functions when an ISDN line is con
`nected to the ISDN U connector, or (iii) ISDN digital voice
`and data processing functions along with ISDN S/T interface
`functions when an ISDN line is connected to the ISDN S/T
`connector. Interface logic couples signals between the DSP
`core and the connectors. A digital data path multiplexer
`coupled between the DSP core and the interface logic
`includes “autosense” logic which monitors signals received
`by the connector coupled to the telephone line and deter
`mines a data transfer mode based upon the received signals.
`The digital data path multiplexer provides the data transfer
`mode information to the DSP core, and the DSP core
`performs communications operations according to data
`transfer mode information.
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2/1991 Davis et al. ............................ 370/463
`4,991,169
`5,305,312 4/1994 Fornek et al. ...
`... 370/264
`5,483,530
`1/1996 Davis et al. .........
`... 370/465
`5,495,485 2/1996 Hughes-Hartogs ..
`... 370/524
`5,602,902 2/1997 Satterlund et al. ......
`... 375/222
`5,671,251
`9/1997 Blackwell et al. ...................... 370/385
`FOREIGN PATENT DOCUMENTS
`0.659 007 A2 6/1995 European Pat. Off. .
`0 772 370 A2 5/1997 European Pat. Off. .
`Primary Examiner—Benedict V. Safourek
`Assistant Examiner—Kenneth Vanderpuye
`Attorney, Agent, or Firm—Conley, Rose & Tayon; Jeffrey C.
`Hood
`
`29 Claims, 4 Drawing Sheets
`
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`Dish
`Exhibit 1012, Page 1
`
`

`
`U.S. Patent
`
`Sep. 29, 1998
`
`Sheet 1 of 4
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`Exhibit 1012, Page 2
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`

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`U.S. Patent
`
`Sep. 29, 1998
`
`Sheet 2 of 4
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`U.S. Patent
`
`Sep. 29, 1998
`
`Sheet 3 of 4
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`Dish
`Exhibit 1012, Page 4
`
`

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`U.S. Patent
`
`sep. 29, 1998
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`Exhibit 1012, Page 5
`
`

`
`1
`COMBINED ANALOG AND DIGITAL
`COMMUNICATIONS DEVICE
`
`BACKGROUND OF THE INVENTION
`
`Field of the Invention
`
`This present invention relates generally to telecommuni-
`cations devices, and more particularly to a combined analog
`and digital communications device which provides sin1ul-
`taneous signal processing at a standard plain old telephone
`service (POTS) two-wire telephone interface, an ISDN U
`interface, an ISDN S/T interface, or asymmetric digital
`subscriber line (ADSL) interface.
`
`Glossary/Related Terms
`23B+D or 30B+D—23 bearer channels and one data/control
`channel carried within a Tl, HDSL or PRI ISDN circuit
`in the USA for example (30 bearer channels in Europe).
`213 +D—two bearer (B) 64 kbps channels and one data,’
`control (D) 16 kbps channel as used in BRI ISDN circuits
`2B1Q—two binary, one quarternary, the line encoding tech-
`nique used in ISDN U interface circuits for example
`ADSL—asymmetric digital subscriber line
`BRI—basic rate interface, comprising 2B+D channels
`CAP—carrierless amplitude phase modulation, a digital
`transmission scheme also used in some pre—standard
`ADSL trials and services
`CCITT—International Telegraph and Telephone Consulta-
`tive Committee (now renamed ITU—T)
`DMT—discrete multitone, a digital transmission scheme
`described by the ANSI T1.413-1995 standard
`DSL—digital subscriber line
`HDSL—high bit rate digital subscriber line. When used to
`carry T1 circuits, uses two twisted-pair (four-wires) to
`carry 1.544 Mbps of digital data bit streams (2.048 Mbps
`over a European E1 line).
`lSDN—integrated services digital network
`ITU—T—International Telecommunication Union—
`Telecommunications Standardization Sector
`modem—modulator, demodulator, the general term applied
`to a communications device that utilizes frequency/phase
`modulation techniques to transport serial digital bit
`streams
`
`PCM—pulse code modulation
`POTS—plain old telephone system
`PRI—primary rate interface
`PSTN—Public Switched Telephone Network
`U interface—two wire ISDN circuit, capable of carrying 160
`kbps of user data (2Fl+I)) over 18 kft of twisted pair _
`wiring between a central office and a subscriber premises.
`V.34—ITU-T V Series Recommendation for a voice band
`modem capable of up to 28.8 kbps over POTS interfaces
`to the PSTN
`xDSL—general term for a high speed DSL, where x may be
`substituted as A or H (as in the ADSL and HDSL cases)
`or other (presently) pre—standard terms such as S
`(symmetrical) or RA (rate adaptable asymmetric)
`
`Description of the Relevant Art
`
`Common analog telephone communications devices
`allow users to exchange both voice messages and digital
`data via analog signals. Analog signals, such as electrical
`voltages or currents, may vary continuously over a specified
`range. The transfer of digital data over ordinary analog
`telephone lines is commonly carried out using analog
`modulator-demodulators (modems). A transmitting analog
`
`_
`
`2
`modern converts a digital value (i.e., a logic one or a logic
`zero) to a corresponding analog signal (e.g., an audible
`tone). A receiving analog modem performs the opposite
`function, converting the analog signal to the corresponding
`digital value. Analog modems are commonly connected to
`personal computers to enable computers to perform com-
`munications functions over ordinary telephone lines. Thus
`digital communications devices such as computers are often
`connected through modems to the “plain old telephone
`system” (POTS), allowing users to communicate with one
`another over long distances via the existing telephone net-
`work.
`Amore modem type of telephone service referred to as the
`integrated services digital network (ISDN) uses digital trans-
`mission schemes that allows users of a telephone network to
`exchange both voice signals and digital data in digital form
`rather than analog, as with POTS. Digital
`transmission
`allows information represented in digital form to be trans-
`mitted across a medium such as twisted pair wiring in a more
`reliable fashion using error correction schemes. For
`example, basic rate ISDN achieves a 160,000 bits per second
`(160 kbps) user bit rate over 18,000 ft. (18 kft) of twisted
`pair. In the case of ADSL, rates of up to 6,000,000 bits per
`second (6 Mbps) over 12 kft and even 51 Mbps over a few
`thousand feet (i.e., short loops encountered in fiber to the
`curb applications) can be accomplished.
`To achieve these higher data rates, ISDN and XDSL
`services require special communications devices having
`ISDN terminal adapters. ISDN terminal adapters are some-
`times referred to as ISDN modems since they perform a
`function analogous to that of analog POTS modems. A
`transmitting terminal adapter forms digital values into pack-
`ets or frames of digital
`information, and transmits the
`packets of digital information using a digital transmission
`scheme which ensures that the serial data stream is delivered
`reliably. A receiving terminal adapter performs the opposite
`function, extracting digital values from received packets of
`digital information. The most important functions carried
`out by the digital transmission scheme include encoding of
`the data into symbols that may be represented with varying
`degrees of frequency and phase, line equalization, cancel-
`lation of signal echoes, bit error rate monitoring, and so on.
`ISDN service provides bearer (ISDN B) channels which
`transmit voice and data in digital form at 64 kbps, and
`signaling (ISDN D) channels which transmit digital data at
`about 16 kbps. The ISDN has two standardized levels of
`subscriber digital access, a basic rate interface (BRI) and a
`primary rate interface (PRI). The BRI provides two ISDN B
`channels and one ISDN D channel (2E+I)), and the PRI
`includes 23 ISDN B channels and one ISDN D channel
`(23B+D) (30B in Europe). The transmission technology
`required for ISDN basic rate access is generally referred to
`as the digital subscriber loop (DSL). Like an analog sub-
`scriber loop, a DSL uses a single pair of wires for both
`directions of transmission between a central office and a
`subscriber’s location. The interface between a communica-
`tions device and a two-wire ISDN transmission line is
`referred to as an ISDN “U” interface. In general, the same
`twisted pair that carries the POTS service is capable of
`alternatively carrying the ISDN or XDSL service, depending
`on the overall quality of the cable plant.
`FIG.
`1
`illustrates how communications devices using
`either analog modems, ISDN terminal adapters, or xDSL
`may communicate via the common public telephone net-
`work using different types of telephone services. In FIG. 1,
`a first communications device 10 includes an analog modem
`connected to a POTS telephone line 12 of a public switched
`
`Dish
`Exhibit 1012, Page 6
`
`

`
`3
`telephone network (PSTN) 14. POTS telephone line 12 is
`typically a pair of wires twisted together (“two wire twisted
`pair”). Asecond communications device 16 also includes an
`analog modem, and the analog modem 16 is connected to a
`POTS telephone line 18 of public telephone network 14. The
`two devices may be connected to the same local telephone
`exchange, or via local exchanges connected by long distance
`trunks. Information is transported across the PSTN in digital
`form and is based on schemes employing multiples of 64
`kbps slots that carry, for example, a single voice conversa-
`tion. First communications device 10 and second commu-
`nications device 16, both having analog modems and POTS
`service, may communicate via public telephone network 14
`at a data transmission rate supported by POTS service.
`Analog modems are currently available for use with POTS
`service which transfer data at a rate of 28.8 kbps using data
`modulation techniques described in the ITU-T V series
`recommendations.
`A third communications device 20 includes an ISDN
`terminal adapter connected to an ISDN transmission line 22
`of public telephone network 14. ISDN transmission line 22
`is typically a pair of wires twisted together similar to those
`of POTS telephone line 12. Third communications device 20
`is supported by ISDN service, allowing digital data trans-
`mission rates of 64 kbps using a single bearer (B) channel.
`From an ISDN viewpoint, the POTS service provided over
`the twisted pair of POTS telephone line 12 is capable of
`supporting voice service only (even though digital data in
`the form of an analog modem signal also uses this voice
`circuit). On the other hand, ISDN services are capable of
`supporting both voice service (compatible with the existing
`POTS) and data service. For the voice class of service, in the
`case of the POTS telephone line 12, the conversion of the
`voice class signal from analog to digital occurs at
`the
`interface to the PSTN, specifically by a line card in the
`central office. In general, the analog stream is converted by
`the line card to a /.t-laW or A-law (country dependent)
`compressed 64 kbps pulse code modulated (PCM) stream.
`An ISDN channel directly carries such a PCM digital stream
`over one of its B channels.
`
`A fourth communications device, ISDN telephone 24, is
`capable of converting the digital PCM signals back to voice
`format, i.e., analog form. D channel signaling from switch-
`ing equipment in the central 0 ice identifies a call from a
`POTS device, such as connnunications device 10, as being
`a voice-type call. In this case, conversion back to analog .
`form by a line card in the centra office is not necessary, and
`is not performed.
`In order to exchange data with POTS communications
`devices which include analog modems (e.g., first commu-
`nications device 10), it is desirable for an ISDN terminal
`adapter to be able to interpret the PCM encoded ITU-T V
`series modem signals correctly. The ISDN terminal adapter
`within third communications device 20 thus preferably
`includes additional circuitry ir1 order to detect and terminate
`or initiate voice originated calls that carry digital data in, for
`example, ITU-T V series form. Such circuitry contains the
`means to decode the analog modem signals either directly
`from the +-law or A-law encoded PCM 64 kbps stream, or
`alternatively by converting them to analog form (as the
`central office does for POTS), and coupling the signals to a
`conventional analog modern device via a built
`in short
`analog loop subscriber line from the ISDN terminal adapter
`itself. The mecl1a11is1n by which V series analog modem
`PCM decoding and encoding may be supported via ISDN is
`described below.
`FIG. 1 also illustrates the mechanics of ISDN—to—ISDN
`via the PSTN and using the data call setup n1ecl1anisn1 in
`
`_
`
`4
`ISDN. This allows higher digital data transmission rates than
`those possible with analog modems and POTS service. Third
`communications device 20 includes an ISDN terminal
`adapter having an industry-standard ISDN S/'1' (four-Wire)
`interface. The ISDN S/T interface includes two pairs of
`wires, one pair for sending information and one pair for
`receiving information. The four wires of the ISDN S/T
`interface of the ISDN terminal adapter are connected to fo11r
`corresponding wires of an ISDN S/T interface of an industry
`standard ISDN network termination (ISDN NT) unit 26 at
`ISDN S/T interface point 28. ISDN NT unit 26 also has a11
`industry-standard ISDN U (two-wire) interface. The ISDN
`L interface includes a single pair of terminals for both
`sending and receiving information to and from the central
`0 ice. The two terminals of the ISDN U interface of ISDN
`NT unit 26 are connected to a pair of wires making up ISDN
`transmission line 22 at ISDN U interface point 23. ISDN
`transmission line 22 is part of public telephone network 14
`and provides ISDN service to ISDN telephone 24. Similarly,
`a fifth communications device 32 includes an ISDN terminal
`
`adapter, this time with an integral ISDN NT unit (i.e., no
`intermediate S/T interface point). The ISDN NT unit
`is
`connected to a pair of wires making up an ISDN transmis-
`sion line 30 at ISDN U interface point 31, providing fifth
`communications device 32 with ISDN service.
`
`When changing a POTS line to ISDN, a change in
`communications equipment
`is required at both the sub-
`scriber end (i.e. an ISDN NT unit is required) and the central
`0 ice (an ISDN U line interface adapter, or an ISDN line
`card, is required). Third commu nications device 20 and fifth
`communications device 32 may communicate using an
`ISDN data connection mode, which provides an unencoded,
`clear 64 kbps channel between the two devices using a single
`B channel, or a 128 kbps channel using two B channels.
`An ISDN NT unit is generally a four—wire—to—two—wire
`interface which performs a defined basic set of communi-
`cations functions and provides physical and electrical ter-
`mination of an ISDN transmission line. It is common for the
`ISDN NT unit to be integrated with other communications
`devices in order to reduce cost. An ISDN NT unit is typically
`incorporated into products such as ISDN terminal adapters
`for personal computer systems. In some cases, an ISDN NT
`1Init may contain additional circuitry to terminate the U
`interface to provide both ISDN S/T and short loop POTS
`subscriber line interface circuit (SLIC), permitting connec-
`tion to legacy POTS phones inside the customer premises.
`Semiconductor devices developed to perform as ISDN NT
`units include the PEB2091 device from Siemens (Santa
`Clara, Calif). Such devices carry out functions such as
`digital—to—analog conversion, analog—to—digital conversion,
`2B1Q line encoding, line echo cancellation and interfaces
`the 2-wire interface to either an ISDN S/I" device, such as
`the Am79C30/32 device from Advanced Micro Devices
`(Sunnyvale, Calif.), or directly to a communications proces-
`sor.
`
`FIG. 1 also illustrates a more modern approach than basic
`rate ISDN. These modern approaches utilize more advanced
`digital transmission techniques, generally referred to xDSL,
`where the ‘X’ indicates a number of different variants of the
`
`service. Asymmetric digital subscriber line (ADSL) is one
`example, which employs a digital
`transmission scheme
`referred to as discrete multitone (DMT), and also a scheme
`referred to as carrierless amplitude phase (CAP) modulation
`(see glossary fore other examples of XDSL). An XDSL
`transmission line 42 employs the same twisted pair as used
`for a POTS or ISDN service. The data rates vary according
`to the length and quality of the line 42. One example is 6.144
`
`Dish
`Exhibit 1012, Page 7
`
`

`
`5
`Mbps in the direction of the user, 640 kbps returned to the
`central oflice (hence the term asymmetric) over 12 kft of
`twisted pair cable. Another is 384 kbps, or even the same
`rates as ISDN (160 kbps), over distances greater than 12 kft.
`xDSL services may not utilize the PSTN, but rather may use
`a data only network such as the Internet or a dedicated
`network for digital video distribution. It is likely however
`that an XDSL communications device 40 could be capable of
`establishing a connection with a POTS or ISDN communi-
`cations device via a bridge to the PSTN. Thus xDSL services
`must be considered a potential candidate for data commu-
`nications. xDSL communications device 40 wfll not contain
`an ISDN NT unit, but will contain a different
`type of
`network termination unit (not shown). XDSL communica-
`tions device 40 is assumed to include the appropriate net-
`work termination unit.
`
`FIG. 2 is a block diagram of a prior art communications
`device 100 capable of selectively performing either:
`ISDN data mode communications with another remote
`ISDN device at rates of up to 128 kbps over the B channels,
`or
`communications over an ISDN subscriber line with a
`slower remote ITU-T V series POTS analog modem device
`at rates governed by the latter device, or (iii) a POTS analog
`modem function over a POTS line. Communications device
`100 may contain a simple ISDN S/T interface to allow it to
`be connected to the ISDN via an external, standalone ISDN
`NT unit which converts the ISDN S/'l‘ interface to a two-
`wire U interface, or it may contain the necessary circuitry to
`interface to the ISDN U line directly.
`Communications device 100 interfaces between one of
`three transmission lines and a host CPU 141. The architec-
`ture of communications device 100 includes several dedi-
`cated functional units for performing various communica-
`tions operations. A first section 110 provides the interface to
`a POTS transmission line. A second section 120 provides
`either a four-wire ISDN S/T interface or an interface to a
`two-wire ISDN transmission line at an ISDN U interface
`point. Athird section 130 provides an interface to a two-wire
`ISDN transmission line at an ISDN U interface point. Thirc
`section 130 is essentially an ISDN NT function similar to
`that
`in an external ISDN NT unit when the ISDN S/T
`interface of 100 is used. Ahost CPU interface 142 is adaptec
`for coupling to a central processing unit or a host device. An
`optional analog modern controller 111 couples to the hos
`CPU interface 142 and provides modem control functions as /
`well as host computer interface functions. Alternatively, a
`host CPU 141 may carry out these functions. A DSP—basec
`modern data pump 112 provides modern data pump (i.e.,
`generates modem data). DSP-based modem data pump 112
`is coupled to a memory unit 113 containing the appropriate _
`DSP instructions and providing DSP storage. DSP-base:
`modem data pump 112 is coupled to modem controller 111,
`or alternately to the host CPU interface 142. DSP—basec
`modem data pump 112 is also coupled to aA/D-D/Aunit 114
`which provides analog-to-digital
`(A/D) and digital-to-
`analog (D/A) conversion. Adata access arrangement (DAA)
`115 is coupled between A/D-D/A unit 114 and a standarc
`POTS two-wire telephone line. DAA 115 provides analog
`modem signals to the standard POTS two-wire telephone
`line. A/D-D/A unit 114 and DAA 115 enable communica-
`tions over the POTS telephone line.
`Second section 120 includes off-the-shelf components
`available today. An optional ISDN controller 121 may
`perform higher layer processing of the D channel than a
`dedicated low level D channel controller 126. In addition,
`ISDN controller 121 may provide additional processing of
`digital data arriving on either of the ISDN B channels. ISDN
`
`6
`controller 121 also provides an interface to the host CPU 141
`via host CPU interface 142. If ISDN controller 121 is not
`present, host CPU 141 may carry o1It
`the higher layer
`functions.
`Either host CPU interface 142 or ISDN controller 121
`couples to a B channel multiplexing device 123 and to a low
`level D channel control device 126 via a microprocessor
`(1IP) interface 122. The B channel multiplexer 123 allows
`the ISDN B channels from the ISDN line, B-1 and B-2, to
`be connected to various bi-directional processing paths.
`Example paths are:
`one or both B channels directly
`through the uP interface 122 to the ISDN controller 121, or
`to host CPU 141, for processing of the B channels directly,
`or (ii) one or both B channels connected to the DSP-based
`modem data pump 112, or (iii) one B channel
`to the
`DSP-based data modem data pump 112 and the other to the
`optional ISDN controller121, or to the host CPU 141. Other
`paths not shown may include a path to a built—in audio
`processor for ISDN telephone applications. The Am79C30
`device form Advanced Micro Devices (Sunnyvale, Calif.) is
`one such audio processor.
`ISDN controller 121 or host CPU 141 is usually respon-
`sible for controlling the B channel multiplexer 123. Both B
`channels are made available to the B channel multiplexer
`123 by an ISDN S/T line interface unit (LIU) 124 coupled
`to an ISDN S/"T DAA 125. The B channels may alternatively
`originate from a direct interface to a built-in ISDN NT unit,
`bypassing the S/T 1.IU 124 and the S/T DAA 125.
`A peripheral interface unit 127 provides the necessary
`conversion between the B multiplexer 123 and an ISDN NT
`interface unit 130. The S/T LIU 124 couples signals from a
`four-wire ISDN S/T transmission line, connected to S/T
`DAA 125, to the B multiplexer 123 and D channel controller
`126. The S,/T LIU 124 contains circuitry for converting the
`C binary signals from the B-1, B-2, and D lines to and from the
`pseudo-ternary coded signals required on the ISDN S/T
`transmission hne, transmitted and received in differential
`line driver format. The S/T LIU 124 also provides bit timing
`recovery, circuitry for detecting logic high and logic low
`marks, frame recovery and generation, collision detection
`for multiple external S/T devices, all in accordance with the
`ITU-T ISDN standards recommendations. The S/T LIU 124
`time division multiplexes the individual B channels and the
`D channels into the ISDN S/T frame structure format that
`appears on the ISDN line.
`The D channel controller 126 processes the 16 kbps link
`access protocol D channel (LAPD) format stream to and
`from the S/T LIU 124. The D channel carries either end to
`end signaling (call setup, tear down information, etc.) or low
`speed packet data. The ITU-T recommendations describe the
`use of this channel in more detail. Typically, the D channel
`controller 126 will perform processing of the level-1 and
`partial
`level-2 LAPD protocol
`(flag detection and
`generation, zero deletion and insertion,
`frame check
`sequence processing for error detection plus some address-
`ing functions. All higher level processing is carried out by
`either ISDN controller 121 or the host CPU 141.
`
`When device 100 has a built-in ISDN NT function 130,
`then the S/T interface is not essential, though may still be
`used to connect to several external S/T terminal devices (not
`shown) allowing them access to the NT function in order to
`interface to the ISDN—U two-wire line. The U line interface
`131 includes specialized signal processing functions and U
`line encoding and decoding functions that allow it to inter-
`face the S/T signals produced by the S/T LIU 124 to a
`two-Wire ISDN U transmission line. As described above, an
`
`Dish
`Exhibit 1012, Page 8
`
`

`
`7
`ISDN communications device may only connect to a central
`office and to the PSTN via an ISDN-U interface line, hence
`it is desirable to integrate this function wherever necessary
`and where local country telecommunications regulations
`allow. ISDN U line interface 131 interfaces either between
`the S/T LIU 124 as shown, or alternatively, via an internal
`digital bus, to peripheral interface 127, bypassing the S/T
`conversion stage. ISDN U line interface 131 couples to the
`ISDN two-wire transmission line Via an analog-to-digital
`and digital—to—analog (A/D—D/A) unit 132 and an ISDN U
`DAA 133. ISDN U line interface unit 131, A/D-D/A unit
`[32, and ISDN U DAA 133 provide the function of an ISDN
`NT unit.
`
`Communications device 100 is configured to selectively
`provide signal processing at a POTS interface, an ISDN S/T
`interface or an ISDN U interface. When both a DSP pro-
`cessing function (e.g., analog modem) and an interface to
`ISDN U are required, for example, unnecessary cost
`is
`introduced today through the use of separate signal process-
`ing devices for different functions. An improved communi-
`cations device and method is desired which selectively
`provides a POTS interface, an ISDN S/'1' interface, or an
`ISDN U interface without increasing the number of func-
`tional units within the communications device.
`SUMMARY OF THE INVENTION
`
`A communications device is presented which is config-
`ured to selectively provide signal processing at a POTS
`interface, an ISDN U interface, or an ISDN S/T interface. A
`first connector allows the communications device to be
`connected to an analog POTS telephone line. A second
`connector allows the communications device to be con-
`nected to an ISDN network at an ISDN U interface point. A
`third connector allows the communications device to be
`connected to an ISDN network at an ISDN S/T interface
`point. A digital signal processing (DSP) core performs:
`analog modem functions when a POTS subscriber line is
`connected to a first POTS connector, or (ii) ISDN digital
`voice and data processing functions along with ISDN S/T
`and U interface functions when an ISDN line is connected
`
`_
`
`to the second connector, or (iii) ISDN digital voice and data
`processing functions along with ISDN S/T interface func-
`tions when an ISDN line is connected to the third connector.
`Interface logic coupled between the DSP core and the
`connectors couples signals between the DSP core and the /
`connectors. A memory unit coupled to the DSP core stores
`software programs and data used by the DSP core. Such
`programs preferably include instructions which implement
`the ISDN communications requirements associated with
`connections to ISDN S/T and U interfaces, and also support
`different
`types of data transfer protocols. Example data
`transfer protocols include simple digital data transfers over
`data mode ISDN connections via the ISDN U or ISDN S/T
`connector and also analog modem emulation functions over
`either ISDN connectors, whereby the DSP simultaneously
`supports both analog modem functions and ISDN U or S
`interface functions. In one embodiment,
`the communica-
`tions device simultaneously supports other two-wire digital
`transmission methods (e.g.,
`those used by ADSL) when
`connections to non-basic rate ISDN two-wire interfaces are
`made over the subscriber loop.
`The preferred embodiment also includes a digital data
`path multiplexer coupled between the DSP core and the
`interface logic. Tl1e digital data path multiplexer includes
`“autosense” logic which monitors signals received by the
`connector coupled to the telephone line and determines a
`data transfer mode based upon the received signals. The
`
`8
`digital data path multiplexer provides information regarding
`the determined data transfer mode to the DSP core. The DSP
`core performs communications operations according to data
`transfer mode information received from the digital data
`path multiplexer. Where a common analog-to-digital and
`digital-to-analog interface to the two-wire subscriber line is
`utilized, such autosense logic may also be present in the
`A/D-D/A unit in order to detect the type of digital transmis-
`sion signals being used on the subscriber line.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A better understanding of the present invention can be
`obtained when the following detailed description of the
`preferred embodiment is considered in conjunction with the
`following drawings, in which:
`FIG. 1 is a diagram illus rating how communications
`devices using either modems, ISDN terminal adapters or
`xDSL devices and having di erent types of telephone ser-
`vices may communicate via the common public telephone
`network;
`FIG. 2 is a block diagram of a prior art communications
`device capable of selectively performing analog modem
`emulation over POTS or ISDN, or ISDN digital voice and
`data communications;
`FIG. 3 is a block diagram of a preferred embodiment of
`a communications device which selectively provides signal
`processing at a POTS interface, an ISDN S/T interface, or an
`ISDN U interface; and
`FIG. 4 is a diagram showing how a single DSP core may
`provide interfacing to a variety of subscriber lines using
`di erent communications protocols and analog or digital
`transmission techniques, depending on the type and nature
`of the subscriber line.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`Incorporation by Reference
`The following references are incorporated herein by ref-
`erence as though fully and completely set forth herein:
`ANSI Tl.60l—l992, ISDN Basic Access Interface for use on
`metallic Loops for Applications on the network side of the
`NT (Layer 1 specification), American National Standards
`Institute, 11 West 42nd St, New York 10036
`ANSI T1.605-1989, Telecommunications—integrated ser-
`vices digital network (ISDN)-basic access for S and T
`reference points (Layer
`1 specification), American
`National Standards Institute, 11 West 42nd St, New York
`10036
`PEB209l Data Sheet—IECQ ISDN Echo Cancellation
`Circuit, Siemens, Santa Clara, Calif., USA.
`ITU-T V34 Recommendations, ITU-T, Geneva, Switzerland
`ANSI T1.413—1995, Network and Customer Interfaces—
`Asymmetric Digital Subscriber Line (ADSL) Metallic
`Interface, American National Standards Institute, ll West
`42nd St, New York 10036
`CCITT Blue Book, Volume III, Fascicle III.8, Integrated
`Service Digital Network (ISDN), “Overall Network
`Aspects and Functions, ISDN User—Network Interfaces”,
`Geneva 1989, ITU-T.
`U.S. Pat. No. 4,991,169, Feb. 5, l99l—Real Time Digital
`Signal Processing Relative to M