Product Note
June 1997

Lucent Technologies L56xMF Host-Based Controller
K56flex™ Modem Chip Set with Integrated PCI-Bus Interface


Lucent Technologies Microelectronics Group PCI Host-Accelerated Modem Chip Set (L56xMF) is the next generation of host-based controller modem solutions. Its high level of integration enables designers to create ultra-low-cost, high-performance, low-power, full-featured modems utilizing a PC host CPU (Pentium*) for the ultimate Windows† 95 or Windows NT solution. The integrated PCI interface allows it to have greater access to host PC system resources. In conjunction with the host PC, it implements K56flex™ technology, with which PC users can achieve Internet connection rates approaching 56 kbits/s with backward compatibility with existing V.34 modems. It also supports host-based V.70 DSVD; video-ready interface, high-speed data modes (V.34 extended rates and fallbacks); Class 1 FAX; SIMULTALK™ FDSP; full-featured TAM; and VoiceView‡ support.

The L56xMF modem provides the optimal parallel interface because as it connects directly with the host PC's PCI bus. This eliminates the 16550 UART bottleneck to allow users to expect virtually unlimited data throughput for higher than conventional data rates.

This chip set offers an on-chip PCI interface that supports both slave and master operation. Extensive bit I/O controls provides hooks for internal and domestic DAAs as well as cellular direct connect.

The DSP hardware performs MIPS-intensive operations, such as K56flex and V.34 and V.32 modulation, while the host performs other less MIPS-intensive functions, such as V.42bis. A host-based controller modem has the benefit of utilizing more powerful CPUs as they become available, as well as access to its plentiful associated RAM and disk space. Users can therefore be updated in the field as code simply resides on the disk. Even with its superior performance, Lucent Technologies host-based controller modems CPU usage is virtually the same as conventional modems.

This high level of integration improves performance while reducing component count. The net result is an overall decrease in total system costs, board space requirements, and power consumption.


Functional Description

The Lucent Technologies L56xMF chip set is a two-chip solution consisting of a Lucent Technologies DSP1645 digital signal processor and a CSP1034AH codec. The DSP1645 is available in a 160-pin MQFP and 176-pin TQFP package. The CSP1034AH is available in a 44-pin MQFP and 48-pin TQFP package. It supports K56flex™, V.34 data (including rates of 33.6 Kbits/s and 31.2 Kbits/s) and FAX rates up to 14.4 Kbits/s. Two additional SRAMs (32K x 8) are needed for K56flex™ operation. An additional audio codec (CSP1027) is required for FDSP/TAM/BA functionality. For two-line support, both the audio codec and the second telephone line codec would be a CSP1027.

The host-based controller solution is compatible with Microsoft's† Windows 95 Telephony Application Program Interface (TAPI) including the Unimodem and Unimodem-V service providers. Off-the-shelf TAPI compliant voice and telephony applications will work in conjunction with this modem solution.

The L56xMF chip set supports two voice modes. The first is IS-101 utilizing <DLE> shielded commands supporting 7.2 kHz, 8.0 kHz, and 11.025 kHz, and both 8-bit and 16-bit samples. Second is a modification to the IS-101 command set. All AT commands are sent through the Com port. The actual voice samples are sent by the wave driver directly to the modem hardware utilizing the PCI bus mastering capability. This mode supports sampling as high as 44.100 kHz (downsampled to 11.025 kHz).

Host-Based DSVD

The host-based DSVD implementation utilizes the host to perform traditional controller functions, speech coding, and multiplexing of voice and data. It supports the ITU V.70 standard including voice activity detection and generation, and volume control for speaker and microphone.

Video-Ready Interface

The video-ready interface supplied by the L56xMF chip set provides videoconferencing capability using traditional POTS lines. The implementation of the ITU-T V.80 standard provides a seamless interface for either software or hardware accelerated ITU-T H.324 implementation. Here again, the host-based architecture of this chip set facilitates future upgrades.


High-performance, hands-free, FDSP support is available with an optional linear audio codec. True full-duplex speakerphone quality allows the user to have a two-way conversation without interrupting the conversation. On top of the ability to independently position the speaker and microphone, Lucent Technologies offers electroacoustic position independence. This offers the designer flexibility with the selection and placement of hardware and supports powered and unpowered speakers to maintain optimal performance.

Utilizing the capabilities of the PCI bus, the L56xMF will support a full-duplex audio stream coming from the Host output mixer being mixed in with local FDSP and down line phone.

The SIMULTALK FDSP supports both variable echo suppression (patent pending) and active noise suppression (patent pending) to ensure stability and eliminate echo to provide the user with an uninterrupted, clear communication path comparable to a handset.

The SIMULTALK FDSP feature uses two echo cancelers: an adaptive hybrid echo canceler and an adaptive acoustic echo canceler. The hybrid echo canceler overcomes the limitations of the interface to the telephone network, while the acoustic echo canceler decouples the microphone input from the speaker output. Automatic gain control on the microphone and speaker allows the user freedom of movement by maintaining a constant volume for transmit and receive modes. A physical adjustment can also be made to the analog volume control at the speaker for user preference. The FDSP firmware operates in either half-duplex mode (switched loss) only or full-duplex mode.

The AEC can be used as a separate module by H.324, and host-based DSVD applications simultaneous with a V.34 connection.

Enhanced Voice Features

The TAM system, which uses the IS-101 command set, can be used in either local or remote mode. In local mode, the user requests to record, modify, manage, or playback messages on the system which actually has stored the data.

While in local TAM mode, the host can monitor ring detect and caller ID. If ringing is present, the host can switch to caller ID mode to decode the caller ID and then choose to pick up in speakerphone mode, or handset, or take a message or receive a FAX. Remote mode allows the user to dial into the TAM system from an outside line to perform similar functions.

TAM mode supports caller ID automatically when the TAM system is in IDLE, record, and playback. The host application can use the caller ID information provided by the modem for user display.

The TAM mode allows concurrent DTMF and tone detection, data/FAX/VoiceView/voice call discrimination, distinctive ring, variable-speed playback, (VSP) and call screening (via speakerphone). Toll-quality VSP supports 2x to half speed variations in 10% increments.

VoiceView allows alternating voice and data over the same line. It can be supported with parallel handset or FDSP.

Integrated DSP1645 with PCI

A ROM-coded DSP1645 digital signal processor (DSP) performs the signal processing and interface to the system bus. The DSP1645 incorporates a PCI interface which supports two full-duplex bus master streams for greater access to host system resources. One PCI stream can be switched between the audio codec interface or the DSP core. The second full-duplex stream supports four word block transfers between system and DSP core.

High-Precision CSP1034AH Codec

The CSP1034AH provides the analog portion of the sigma-delta technology modem codec. Because the high-precision analog codec is separate from the rest of the digital circuitry, users can more easily implement homologation and docking-station type applications.

The CSP1034AH supports both optical and transformer DAAs and eliminates a significant number of components, resulting in less board space and lower system cost.

Extensive Bit I/O Control

The 24-bit I/O pins support domestic and international DAAs with hooks for serial EEPROM DAA identification. In addition, control pins are available to support VoiceView applications.

Low-Speed Crystal Support

By incorporating a PLL, this chip set can support low-speed external crystals. This means that minimizing EMI is much easier and low-cost crystals can be utilized. If future code needs higher clock rates, an internal multiplier can provide this without redesign or rectification of the external hardware.


Figure 1. Lucent Technologies L56xMF Host-Based Controller Modem Chip Set Block Diagram

Package Information


Figure 2. L56xMF Chip Set Package Option

Mars and SIMULTALK are registered trademarks of Lucent Technologies Inc.
K56flex is a trademark of Lucent Technologies Inc. and Rockwell International.

* Pentium is a registered trademark of Intel Corporation.
Windows and Microsoft are registered trademarks of Microsoft Corporation.
VoiceView is a registered trademark of Radish Communications Systems, Inc.
§ MNP is a trademark of Microcom, Inc.

Literature Requests and Additional Information

To order this document, use order code: PN96-053DMOD

Copyright © 1997, 1998 Lucent Technologies. All rights reserved. Trademarks

Back to: [ K56flex™ Home ]