off, low, typical, and high. The SerDes block also supports
loop-back modes and advanced reporting of error
conditions, which enables efficient debug and management of
the entire system.
Flexible Port Configurations
The PEX 8619 supports a large number of port configurations
as shown in figure 1 below. Please refer to the PEX 8619
datasheet for more port configuration options.
Port and Virtual Channel (VC) Arbitration
The PEX 8619 switch supports hardware fixed and Weighted
Round-Robin Ingress Port Arbitration. This allows fine tuning
of Quality of Service and efficient use of packet buffers for
better system performance. The PEX 8619 also supports WRR
VC arbitration scheme between the two virtual channels.
Applications
Suitable for fan-out, control plane applications, embedded
systems as well as intelligent I/O applications, PEX 8619
can be configured for a wide variety of form factors and
applications.
Figure 1. PEX8619 Port Configurations
Fan-Out
The PEX 8619 switch, with its high port count and flexible
configurations, allows user specific tuning to a variety of host-
centric as well as peer-to-peer applications.
Hot-Plug for High Availability
Hot-Plug capability allows users to replace hardware modules
and perform maintenance without powering down the system.
The PEX 8619 Hot-Plug capability feature makes it suitable
for High Availability (HA) applications. If the PEX 8619 is
used in an application where one or more of its downstream
ports connect to PCI Express slots, each port’s Hot-Plug
Controller can be used to manage the Hot-Plug event of its
associated slot. Every port on the PEX 8619 is equipped with
a Hot-Plug control/status register to support Hot-Plug
capability through external logic via the I2C interface.
Dual Cast
The PEX 8619 supports Dual Cast, a feature which allows for
the copying of data (e.g. packets) from one ingress port to two
egress ports allowing for higher performance in storage,
security, and mirroring applications.
Read Pacing
Figure 2. Fan-in/out Usage
The Read Pacing feature allows users to throttle the amount of
read requests being made by downstream devices. In the case
where a downstream device requests several long reads back-
to-back, the Root Complex gets tied up in serving this
downstream port. If this port has a narrow link and is therefore
slow in receiving these read packets from the Root Complex,
then other downstream ports may become starved – thus,
impacting performance. The Read Pacing feature enhances
performances by allowing for the adequate servicing of all
downstream devices by intelligent handling of read requests.
Figure 2 shows a typical fan-out design, where the processor
provides a PCI Express link that needs to be fanned into a
larger number of smaller ports for a variety of I/O functions,
each with different bandwidth requirements.
In this example, the PEX 8619 would typically have a 1-lane
upstream port, and as many as 15 downstream ports. The
downstream ports provide x1 PCI Express connectivity to the
endpoints. With its sixteen ports, the PEX 8619 can provide
fan-out connectivity to up to fifteen PCI Express devices. The
figure also shows how some of the ports can be bridged to
provide PCI slots or Generic devices through the use of the
PEX 8311 and PEX 8112 PCIe bridging devices.
SerDes Power and Signal Management
The PEX 8619 provides low power capability that is fully
compliant with the PCI Express power management
specification. In addition, the SerDes physical links can be
turned off when unused for even lower power. The PEX 8619
supports software control of the SerDes outputs to allow
optimization of power and signal strength in a system. The
PLX SerDes implementation supports four levels of power –
Control Plane Application
The PEX 8619 is ideal for control planes in routers and other
communications sub-systems to meet increased packet
processing needs without compromising latency. Figure 3
shows a controller card with a PEX 8619 connecting the
PLX [ PLX TECHNOLOGY ]
