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Adaption Layer Controller ALC
The MB86687 is an ATM protocol controller which autonomously terminates ATM
Adaptation Layer standards Type 3/4 and Type 5. Streaming and message modes as
defined for AAL 3/4 and AAL5 are supported. User data packets are transferred to and
from shared data structure memory via a high speed intelligent DMA controller with a 32
bit data Bus. The device supports simultaneous segmentation and reassembly on up to
1024 virtual circuits (VCs).
Shared data structures are stored in SAR memory which can be either dual-port or a
partition of system memory. Segmentation packets and packets being reassembled may
also be stored in dual-port memory. In addition external data structures are also stored in
SAR memory and may be accessed via the DMA controller. In non-demanding
applications, system memory can be used as SAR memory.
The ALC device supports two transparent modes. In transparent payload mode the 48
byte ATM cell payload is received or transmitted transparently into or from SAR memory.
In transparent cell mode the ATM cell is received or transmitted transparently into or from
Other features include:
The leaky-bucket algorithm is used to shape the transmit data characteristics on a
per-virtual-circuit basis by controlling the average rate of cell transmission and the length
of each burst of cell generated.
In addition to the traffic shaping applied to the traffic transmitted from each virtual circuit,
the ALC can manage both the peak and average transmission rate on the total ALC output
- Support for up to 12 peak segmentation rates with sub-ratios of 0.5 and 0.25 of peak
- rates selectable on a per-VC basis
- Programmable peak and average rates with leaky-bucket averaging on total ALC
- cell stream output.
- UTOPIA v2.01 Compatible cell stream interface with optional HEC checking on receive and HEC octet disabled modes
- Flexible routing tag append / remove mode for direct ATM Switch connection
- Supports Intel and Motorola modes, including line transfers (i.e. single cycle bursts)
- Internal cache to store header info and traffic parameters for up to 128 VCs
- Packaged in 208-pin plastic quad flat pack
- JTAG complient
In adapter card applications, the ALC interfaces to the Fujitsu MB86683 NTC or other
device via a full duplex 8 bit wide UTOPIA compatible cell stream interface for connection
to the transmission medium. In a hub or router application, the ALC connects directly to
the Fujitsu MB86680 SRE for autonomous routing. In this case a programmable 0-3 byte
tag can be appended to each cell. Alternatively it may be connected to a proprietary
Technology: || unknown|
Package: ||PQFP 208 Pin|
PDF documentation used to be available at: http://www.fml.co.uk/flyer/87a_fly.pdf
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