TNETA1575 datasheet(41/45 Pages) TI1

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TNETA1575

ATM SEGMENTATION AND REASSEMBLY DEVICE

WITH PCI-HOST AND COPROCESSOR INTERFACES

SDNS040C – MAY 1996 – REVISED JUNE 1998

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATIONS INFORMATION

introduction

The TNETA1575 implements a range of features targeted for cell-operating enterprise hubs. The growth in

acceptance of ATM in the backbone transfers quickly to the backplane (the collapsed backbone). The

TNETA1575 also is suited for lower-cost applications such as stackable hubs. The growth in acceptance of ATM

in the backbone can lead to an increase in demand for ATM connectivity in the installed base of stackable

classical-LAN operating products.

To support these applications, a different SAR architecture is required that includes the following characteristics:

• Cell interface that can go beyond 155-Mbit/s transfer rates. This increases the number of front-end

legacy interfaces that can be supported by a single SAR device.

• Direct support for constant-bit-rate (CBR) traffic via a dedicated input, a scheduling mechanism and

priority-queue scheme make isochronous services available to enterprise hubs and to stackable hubs.

The connection parameter cell-delay variation tolerance (CDVT) is not supported by the TNETA1575

scheduler.

• Supportforthefullrangeofvirtualpathsandvirtualchannels,and2K-ABRchannelsthatarerequiredto

enable the deployment of large and scaleable virtual LANs

• Support for an internal scheduler. The COPI is used to interface to an external scheduler, which would

provide support for all the ATM classes of service.

• High-performance features. On the transmit side, these include the transmit-channel sleep mode,

which prevents polling of transmit channels with no data queued. On the receive side, these include

features that utilize PCI-bus sideband signals to eliminate polling across the PCI bus completely.

• Early segmentation. This is very important to systems that require reduced latency (isochronous hubs).

Early segmentation enables multimedia applications to take full advantage of ATM facilities.

• Support for the full range of virtual paths and virtual channels. This is a requirement for the collapsed

backbones that are a part of virtual LANs, and the feature offers support for multimedia applications.

• An option to program the UTOPIA-cell interface as either a PHY or ATM-layer system. This option

provides the TNETA1575 a capability to function as a PHY where the cell switch is distributed or as an

ATM-layer interface for adapter cards or ATM uplinks.

system-level overview

The TNETA1575 and the TNETA1585 provide a flexible, high-performance solution that implements the ATM

forum’s available-bit-rate (ABR) service category, as specified in the ATM-forum traffic management 4.0

interoperability specification. A summary of these two devices follows:

TNETA1575 HyperSAR-PLUS

The TNETA1575 is a SAR engine based on TI’s TNETA1570 architecture. Its primary interfaces are:

• 32-bit PCI for host transfers

• UTOPIA for cell transfers

• COPI for traffic-COP flow-control management

• Control memory for status information

• Local-bus interface for accessing the PHY device via the SAR

TNETA1575 数据表(PDF) 41 Page - Texas Instruments

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