This device, called the Meteor, provides MPEG support for multimedia applications and provides end-to-end connections with a high quality of service. It is targeted for high-speed, high-bandwidth servers and switches connecting legacy LANs to the ATM backbone. Meteor is fully compliant with the latest ATM specifications for UNI 4.0, which means that it is the first to support Constant Bit Rate (CBR), Available Bit Rate (ABR) and Unspecified Bit Rate (UBR) service classes. It also contains some unique features, such as MPEG2 packet transmission support and a credit-based flow control option that provides extra reliability on an ATM network by minimizing cell loss. Meteor also uses host memory-based frame segmentation and reassembly, which leads to savings in local memory costs.
The TC35856F supports the PCI bus and the Universal Test and Operations Physical layer Interface for ATM (UTOPIA). The device interfaces to the 33MHz, 32-bit PCI bus following the PCI Local Bus Specification, Revision 2.1, to provide high performance, lowlatency data transmission. Its PHY interface implements the standard UTOPIA Level II interface specification of an 8-bit interface running at 33MHz. The chip also supports a reversible UTOPIA mode of operation, allowing the device to be connected to the switch fabric through the same mechanism as all other ports in the switch.
Meteor contains a DMA engine that sends the protocol data units (PDUs) to and from the host memory for segmentation and reassembly. This design eliminates the necessity for large amounts of memory on the adapter. For example, the device requires only 128 kilobytes (KB) of on-board, 15 nanoseconds SRAM to support 1,024 transmit and receive VCs simultaneously, and 64KB SRAM to support 256 VCs.
Meteor supports segmentation and transmission of up to 1,024 AAL5 PDUs simultaneously with AAL5 Cyclic Redundancy Check (CRC) generation. The IC segments AAL5 PDUs, appends the cell headers to each ATM cell created by the segmentation process, computes AAL5 CRCs, and writes the computed CRCs in the transmitted PDUs. It can reassemble 1,024 AAL5 PDUs simultaneously in the receive direction and verifies the AAL5 CRC.
Meteor provides full performance at Synchronous Transport Signal Line 3 (STS-3c) line rates (155Mbps). It provides full support for the ATM Forum UNI 4.0 traffic management specifications, including CBR, ABR and UBR. Meteor generates and processes ABR RM cells and provides per-VC rate control without host-driver intervention. Support for other classes of service is provided via raw 52-byte cells.
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