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To: bill c. who wrote (11355)	6/8/1998 8:17:00 PM
From: bill c.	Respond to of 21342

[ TI - March Article ] Networking Chips -- Three TMS320C6-based sets target PCI, client-side modems, central offices -- TI samples its first merchant silicon for ADSL By Loring Wirbel Dallas - Texas Instruments Inc. is sampling three separate TMS-320C6x-based chip sets for three distinct applications of asymmetric-digital-subscriber-line technology. The offerings constitute TI's first merchant silicon for ADSL. The TNETD2000P is for client-side PCI applications, the TNETD2000R is for embedded client-side ADSL modems, and the TNETD2000C is for telephone central-office support of multiple lines. The chip sets are compliant with Issue 2 of ANSI's T1.413 standard for ADSL. At the heart of all three is an ADSL transceiver that uses a TMS320C6x core running echo-cancellation discrete multi-tone algorithms. The DMT algorithms are based on work by Amati Communications Corp., which TI acquired in 1997. James Collinge, DSL product marketing manager at TI, observed that most DMT transceivers use frequency-division multiplexing to achieve multiple modulation channels over one copper wire. TI's use of echo-cancellation DMT, Collinge said, will provide an edge in improving performance. All of the chip sets, while varying in functions and features, encompass the transceiver, a digital interface chip, a codec and a high-frequency line driver. All of the offerings support speeds of up to 8 Mbits/second downstream and 800 kbits/s on the return path over 9,500-foot copper loop lines. TI claims to offer the only DSP chip that can support multiple lines from one device for central-office applications, though Lucent Microelectronics and Analog Devices Inc. both plan to offer dedicated central-office DSPs. Up to four lines can be handled by one TI ADSL transceiver running full-rate ADSL, and twice that many subrate ADSL lines can be supported. The first-generation chip sets support dual lines per DSP, but a quad device slated for 1999 delivery will double the number of supported lines. The 14-bit, 2.2-Msample/s codec and the high-voltage line driver were developed in conjunction with Amati. That company's engineers continue to work directly with TI DSP developers in adopting the Amati line codes for the emerging "splitterless" standards developed by the G.Lite working group. The TNETD2000C central-office chip set avoids hardware upgrades for telephone companies looking to roll out ADSL support, since code fixes and enhanced software for splitterless ADSL G.Lite can be downloaded into existing processors, even remotely. TI's near-term task for upgrading central-office hardware will be to add asynchronous-transfer-mode support for the digital interface-particularly multiple ports of Utopia interface and transmission convergence functions-on a peripheral chip. Other functions to be added to a central-office set include Ethernet; high-level data link control; and support for the Universal Serial Bus, IEEE 1394 FireWire and Peripheral Component Interconnect. TI also will poll its customers on desired software features, such as routing/bridging protocol stacks, encryption and network management. "It may make the most sense to provide application programming interfaces so that customers can add their own software," Collinge said. "But we will consider all options for enhancing the software set." The TNETD2000R and 2000P sets were easier to define. The 2000R provides the most stripped-down levels of direct ADSL access functionality, for systems that will be embedded in network-termination external modems. For the 2000P, intended for PC-based PCI designs, TI is providing a PCI interface and includes an ATM host interface controller with embedded segmentation/reassembly (SAR) processing as part of the chip set. Windows 95/NT drivers are also included. Upgrades of the chip sets for G.Lite, or even a future very high-bit-rate DSL (VDSL), will not require changes in either the transceiver or the digital interface chip. Instead, new firmware can be added to the transceiver, and special analog front-end cards can be designed for the line end of the transceiver, allowing support of multiple DSL types, according to the company. On the subscriber end, TI is heeding requests from OEMs to have the core C6x DSP handle analog V.90 modem functions as well as DMT ADSL, and is designing a chip set with such functions in mind. The current four-chip set, implemented in 0.25-micron CMOS, typically dissipates 4 W, with the smallest line-driver device consuming the biggest portion of the power budget. A decrease in power consumption is expected when TI migrates to 0.18-micron CMOS. Collinge asserted that many competitors tout artificial power budget numbers that do not take into account all portions of an ADSL system. The suggested resale price for the TNETD2000C in quantities of 25,000 is $95 per set. The TNETD2000P in similar quantities is $76 per set; the embedded TNETD2000R is $65.