NSE-20G™ Standard Product Data Sheet
Preliminary
6 Description
The PM8620 NSE-20G is a monolithic CMOS integrated circuit packaged in a 480 ball UBGA
that performs DS0 and above granularity space switching on 32 SBI336 streams carried as serial
SBI336S in 8B/10B coding over LVDS at 777.6 Mbit/s. The NSE-20G also performs VT1.5/VT2
and above granularity switching on 32 STS-12/STM-4 SONET/SDH streams, carried as Serial
TelecomBus signals in 8B/10B coding over LVDS at 777.6 Mbit/s.
The NSE-20G is typically used with up to 32 PM8610 SBS or PM8611 SBS-lite devices to
provide Memory-Space-Memory switching systems. As each SBS supports either four SBI buses
at 19.44 MHz or one SBI336 bus at 77.76 MHz, the overall system supports any mixture of SBI
and SBI336 byte serial buses, ranging from 128 19.44 MHz SBI buses to 32 SBI336 77.76 MHz
buses that do not exceed an aggregate bandwidth of STS-384, or about 20 Gbit/s. In TelecomBus
mode, the SBS devices support the same range of flexibility for 128 19.44 MHz and 32 77.76
MHz TelecomBuses at VT1.5/VT2 granularity
Central to the NSE-20G is a 32 x 32 cross bar switch. At every clock cycle, the cross bar
switches a byte of data with control signals from each input port to an output port. The byte of
data may be a DS0 channel from a T1/E1 or may be one byte of a column comprising a T1, E1,
DS3, E3, VT1.5, VT2 or STS-1.
In order for switching to take place all input and output streams must be synchronized. This is
done via the RC1FP input signal. When switching T1s, E1s, VTs and other higher order units only
SBI336 multiframe alignment is required. The same applies for TelecomBus mode where only
frame alignment is required.
An in-band control link over the serial LVDS interface allows the NSE-20G to communicate with
the microprocessors attached to the SBS, SBS-lite or other serial SBI336S devices. The effective
bandwidth of each inband link to each device is 8 Mbit/s. The inband link provides error
detection on 32-byte user messages and some near realtime control signals between devices.
Using the near realtime control signals, the NSE-20G is able to synchronize page switching,
indicate switchover between working or protected links, and exchange three user defined signals
(software) and 8 Auxilliary signals (software). The user and auxilliary signals can be used to
indicates interrupts or initiate handshaking between the end point microprocessors. The message
format is left to the user of the devices. The only constraint is that each message is a maximum of
32 bytes long.
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
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Document ID: PMC-2000170, Issue 3