Electronic Design

Processor Eases Inexpensive Internet-Protocol Phone Design

The Audacity-T2 IP Telephone Processor combines all of the digital-processing circuitry required for a full-function, Internet protocol (IP) telephone on one chip. Telephony-equipment manufacturers can use it to build cost-effective, high-quality phones for broadband IP network applications.

All of the software required for IP voice communication is provided with the device. OEMs also get all of the control protocol stacks and audio codecs required for IP telephony systems. The T2 processor can run two simultaneous calls using any of the supported codecs while executing full-duplex echo-cancellation algorithms and a control protocol stack.

It's built around the MIPS-X5 unified RISC CPU/DSP engine, which is designed to efficiently run both compiled "C" code and DSP algorithms. The processor also incorporates a 32-channel DMA engine and a nonblocking crosspoint switch with 6.4 Gbytes/s of cross-sectional memory bandwidth, ensuring optimal system performance. Sufficient on-chip memory is provided to eliminate the need for external RAM when running any supported communication protocol or codec.

The T2 also incorporates dual Ethernet media access controllers (MACs)—one for connecting to a network, and one for connecting to a computer. The inclusion of MAC functionality enables an IP telephone to serve as a two-channel layer-2 Ethernet switch, eliminating the need for two Ethernet connections to the desktop. Such a switch facility can be programmed to give priority to audio packets, buffering data packets to and from the attached PC. This controls quality of service (QoS). The full-duplex MACs support both 10- and 100-Mbit/s data rates.

Eliminating the need for expensive glue logic, the processor connects directly to network physical-layer chips, keypads, and character display devices. Two time-division-multiplexed (TDM) ports provide multichannel synchronous interfaces for audio data, permitting connection to a telephone handset or to a microphone and speaker for speakerphone implementations.

A complete IP phone development kit also was developed. It includes two fully operable IP feature phone prototypes, a developer's version of the IntraSwitch IP-PBX server software, and all of the documentation required to build the phones.

Developers can customize and differentiate their products with the company's source code for the user interface and device drivers. It also has a complete development environment, featuring a compiler, a debugger, and diagnostic software. The resulting package includes everything, from the chip to the software tools, needed to bring cost-effective, high-quality IP phones to market.

The Audacity-T2 IP Telephone Processor is packaged in a 176-pin, thin quad flat package (TQFP). The chip, manufactured in a 0.18-µm, 1.8-V CMOS process with 3.3-V interfaces, dissipates an estimated 0.25 W in full operation. Samples (part number 8x84700) are now available. It's priced at $15 each in 100,000-unit volumes. Software-development tools and IP-telephone design examples also are available.

8x8 Inc., 2445 Mission College Blvd., Santa Clara, CA 95054; (408) 727-1885; (408) 980-0432; www.8x8.com.

TAGS: Components
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