South
Bridge
Scanner
PCIe Slot or
Cable
End Point
PEX 8505
x1
Proprietary
ASIC
x1
Stereo
CODEC
VIA
17242
PCI
Bus
PEX 8111
Processor
x1
PCIe Sound Card
PEX 8505
x1
x1
PCIe TV Tuner Card
Philips
Hybrid
Tuner
IF
CVBS
2IF
Conexant
CX23882
PCI
Bus
Ethernet
Proprietary
ASIC
Marking Engine
Conexant
Demod
CX22702
TS
PEX 8111
Figure 3. I/O Expansion
Video Surveillance
A video surveillance application is another example for an
embedded application. When used together with a PEX8311,
PCI Express-to-local bus bridges, the PEX8505 can connect to
other embedded devices, such as FPGAs. This allows video
capture devices to interface to a PCI Express host taking
advantage of the PCI Express performance. For more
information on the PCI Express-to-Local Bus bridge, please
visit PLX’s website at
www.plxtech.com/bridges.
Camera
CPU
Figure 5. Printer Engine
Software Usage Model
From a system model viewpoint, each PCI Express port is a
virtual PCI to PCI bridge device with its own set of PCI
Express configuration registers. It is through the upstream port
that the BIOS or host can configure the other ports using
standard PCI enumeration. The virtual PCI to PCI bridges
within the PEX 8505 are compliant to the PCI and PCI
Express system models. The Configuration Space Registers
(CSRs) in a virtual primary/secondary PCI to PCI Bridge are
accessible by type 0 configuration cycles through the virtual
primary bus interface (matching bus number, device number,
and function number).
Camera
JPEG
FIFO
FPGA
PEX 8311
Camera
.
.
CPU
JPEG
FIFO
FPGA
PEX 8505
Control
Processor
Interrupt Sources/Events
The ExpressLane PEX 8505 switch supports the INTx
interrupt message type (compatible with the PCI 2.3 Interrupt
signals) or Message Signaled Interrupts (MSI) when enabled.
Interrupts/messages are generated by the PEX 8505 for hot
plug events, baseline error reporting, and advanced error
reporting.
Camera
Camera
PEX 8311
Camera
Figure 4. Video Surveillance
Printer Application
In a printer application, low power and low latency devices are
commonly used. Figure 5 shows an example of a printer
application. In this example, the low power processor used
provides a limited number of PCI Express ports. The PEX
8505 can be used to provide four additional PCI Express ports
for the connectivity of other system peripherals such as
Ethernet as well any proprietary PCI Express based ASICs.
The Peer-to-Peer feature in the PEX 8505, allows a peripheral
connected on a downstream port the ability to transfer data
directly to another peripheral device. As shown in Figure 5,
the ASIC connected to the scanner side can transfer data
directly to the PCIe Slot and/or the ASIC connected on the
Marking Engine side resulting in a low latency data transfer.
In this case, the processor is not directly involved in the
transfer.
www.plxtech.com
PLX [ PLX TECHNOLOGY ]
