RELEASED
PMC-Sierra, Inc.
PM9311/2/3/5 ETT1™ CHIP SET
Data Sheet
PMC-2000164
ISSUE 3
ENHANCED TT1™ SWITCH FABRIC
4
Crossbar
This chapter contains information on the Crossbar device, part number PM9312-UC, available from
PMC-Sierra, Inc.
The Crossbar device is a multicast-capable, 32-port, reverse-routed Crossbar. Each Crossbar is
connected to the matching logical Dataslice in every port. For example, XBAR0 connects to DS0. Each
Crossbar switches an eight byte cell each frame time.
The device sets its crosspoints according to the reverse routing tags supplied by the Scheduler, via the
EPPs and Dataslices. If the routing tag supplied is non-valid, the frame containing cell data being sent to
this DS had a CRC error, or the frame containing the routing tag from this DS had a CRC error, then the
VLD bit is not set on the frame to the DS.
4.1 CROSSBAR BLOCKS
Figure 62 shows the basic data flow through the Crossbar. The routing tag sent in the AIB frame from the
Dataslice is registered in the routing tag register (RTR). The RTR selects one of the 32 incoming byte-wide
busses and the output of the 32:1 byte-wide mux is driven to the transmitter side of the asymmetric serial
link dumb end.
The total delay from d2x_p[31:0] to x2d_p[31:0] is four cell times.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
225
PMC [ PMC-SIERRA, INC ]
