Chapter 4 Functional Overview
4.1
PEX 8532 Architecture
The PEX 8532 switch is designed with a flexible, modular architecture. The two main building
blocks of this architecture are the non-blocking Crossbar Switch fabric (internal fabric) and
protocol-specific I/O module, termed station. Figure 4-1 illustrates a block diagram of the PEX 8532.
Figure 4-1. PEX 8532 Block Diagram
Station 0
Port 0
Station 1
Ingress
Egress
Scheduler
Scheduler
Lanes
Lanes
Crossbar
Switch
Egress
Crossbar
Switch
Ingress
Internal
Fabric
PCI Express
Upstream
Station 0
PCI Express
Downstream
Station 1
Crossbar
Switch
Egress
Crossbar
Switch
Ingress
Ingress
Scheduler
Egress
Scheduler
4.1.1
Ingress and Egress Functions
The Crossbar Switch Ingress queue interfaces the PCI Express station to the internal fabric. The queue
contains a centralized packet buffer for incoming ports, ingress port scheduler, and internal
fabric scheduler.
The Crossbar Switch Egress queue interfaces the non-blocking internal fabric to the PCI Express
station. The queue contains a centralized packet buffer for all outgoing ports and the egress
port scheduler.
All ingress traffic flows from the PCI Express station by way of the Crossbar Switch Ingress queue,
internal fabric, Crossbar Switch Egress queue, and finally to the outgoing PCI Express station. Ingress
and egress scheduler modules contain a Virtual Channel (VC) scheduler for each port. The ingress
scheduler supports a port-width-based arbitration scheme. The egress scheduler supports a
device-specific port arbitration scheme, to avoid port starvation.
ExpressLane PEX 8532AA/BA/BB/BC 8-Port/32-Lane Versatile PCI Express Switch Data Book
Copyright © 2007 by PLX Technology, Inc. All Rights Reserved – Version 1.6
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