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ST70134-ST70135A Datasheet(PDF) 2 Page - STMicroelectronics |
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ST70134-ST70135A Datasheet(HTML) 2 Page - STMicroelectronics |
2 / 8 page ST70134 - ST70135A 2/8 GENERAL DESCRIPTION The ADSL modem chip set with ATM interface provides all the active functions required to build a complete ATM-based ADSL modem from line interface to ATM UTOPIA bus. The chip set employs Discrete MultiTone modulation as specified in ANSI T1.413. The chip set operates at CPE end of the loop (ATU-R mode). Reed-Solomon forward error correction plus Trellis coding with or without interleaving in internal interleaving RAM provides maximum noise immunity (see Figure 3). Interleaving is optional and can be used simultaneously on a slow channel (e.g., for data or control info) while a fast channel (e.g., video) operates without interleaving. ICs include rate adaptation capabilities during show time. In transmit direction the chip set allows to select an attenuation of the signal in case of short loops or large echo (politeness). In receive direction the chip set can optionally control an external multiplexer to select an external attenuation of the signal in case of short loops, and provide a 2-bit output external gain control. ASCOT chip set ASCOT is a two-chip ADSL modem transceiver. STMicroelectronics provides the necessary software for transceiver’s external controller. ASCOT can easily be hooked up with ATM systems through the built-in UTOPIA level 2/1 interface. That allows ATM traffic to be carried at up to 8Mbit/s downstream and 1Mbit/s upstream, over a very plain and widespread twisted pair. ASCOT is intended for use at ATU-R end. The modem control software can be compiled as C++ code, independently on the processor used. The driver can be interfaced to any external real time operating system. These pages block diagrams show the main functions built-in in ST70134 and ST70135A. ASCOT chip set supports three different rate adaptation modes: fixed rate adaptation mode, fixed with capability to boost within fixed range, dynamic rate adaptation during show time. Modem’s performances are set by the following parameters: Rate adaptation mode, Downstream and Upstream bit rate for both latency paths, Noise margins (min, max and target typically at 10E-7 BER without RS, interleaving and trellis), Maximum power spectral density for downstream, Maximum power for both up and downstream, Carrier mask (which tones are disabled), maximum interleaving delay. Tones from number 8 to number 255 can be used: from 8 to 31 for upsteam signals and from 32 to 255 for downstream signals. Numbers 16 and 64 (96 for ADSL over ISDN) are dedicated to pilot tones which are employed for synchronisation purposes with ATU-C end. The software sets the use of tones for optimisation of performances. Time recovery is carried out by the chip-set through the pilot tones. This activity is undertaken in two steps in order to achieve no more than 2ppm with ATU-C. The transceiver controller software monitors line and channel. As far as line is concerned noise margin, attenuation, power, carrier load, relative capacity occupation are checked. Channel’s monitoring deals with cell-delineation, actual ATM (fast and interleaved) up and downstream rates. Figure 1 : ADSL modem block configuration DMT MODEM ST70135A UTOPIA µ CONTROL MEMORY AFE ST70134 χ χ UTP |
Número de pieza similar - ST70134-ST70135A |
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Descripción similar - ST70134-ST70135A |
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