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622 Mbit/s SAR controller
Hitachi's 622-Mbit/s cell-processing solution is the NewPort
architecture. This chipset is comprised of the HD64556 hardware
accelerator and a Hitachi SH-3 RISC processor. The set does
full-duplex 622 Mbits/s over ATM, hardware accelerating on the
MPOA and LANE standards, and full hardware-based QoS
function. It also handles CBR, VBR and ABR classes of service.
The HD64556 chip doesn't integrate the MPOA protocol
on-chip, but rather accelerates the MPOA and other standards.
Hitachi plans to follow its 622-Mbit/s ATM announcement with a
155-Mbit/s solution having the same basic architecture.
Although ATM is a cell-based protocol, the NewPort architecture
handles both cells and packets. The latter can be either IP or
frame-relay type. According to Hitachi, a number of designers
have expressed interest in using it as a packet engine to handle IP
packets at 622 line rates.
Connection to the physical layer takes place over a standard ATM
UTOPIA interface. By necessity, the 622-Mbit/s connections are
through an optical fiber connection. The UTOPIA, however,
allows connection to quad OC-3 155 ports. Alternatively, one
could connect to four 155-Mbit/s connections over analog UTP
Cat 5 twisted-pair wires. At the other end of the NewPort
architecture is a 66-MHz PCI interface. This connects into the
backplane of the customer's switch and its host CPU.
Key to the NewPort architecture is a separate SH-3 RISC
processor. The SH-3 handles tasks that aren't directly related to
cell processing. This processor lies outside the packet or cell data
flow. It sits off of a separate bus accelerator implemented in a glue
chip (an EPLD). This glue chip separates the buses, allowing
maximum memory bandwidth on the 64-bit local bus connected
to the hardware accelerator, while the SH-3 performs
batch-oriented processing and resource cell management. In
ATM systems using the ABR class of service, the flow of cells can
be adjusted when network congestion occurs. An RM (resource
management) cell is sent from the source to the destination, and
back up from the destination to the source, telling it to "slow down
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