PEX8508-AC25BI G PLX Technology, PEX8508-AC25BI G Datasheet - Page 3

• Manufacturer Part Number: PEX8508-AC25BI G
• Description: Communications IC
• Manufacturer: PLX Technology

Specifications of PEX8508-AC25BI G

• Termination Type: SMD
• Control Interface: I2C, Serial
• Communication Function: PCIe Switch
• Package / Case: 296-PBGA
• Rohs Compliant: Yes
• Filter Terminals: SMD

The PEX 8508 can be used to create an adapter card that
aggregates the PCI Express devices into a single port that can
be plugged into a backplane or a motherboard. Figure 3
shows the PEX 8508 in this application.
The adapter card in Figure 3 is transparent with no local
processor present. Here four Gigabit Ethernet (GE) ports are
aggregated through the switch. Recent MAC/PHY devices for
GE all well as InfiniBand, Fibre Channel, etc., have native
PCI Express support for direct connections to the switch. The
non-blocking low latency design of PEX 8508 provides full
throughput with latency under 150ns.
Intelligent Adapter Card
The PEX 8508 supports the non-transparency feature. Figure 4
illustrates an intelligent adapter card used in servers and
storage hosts and is commonly used in TCP/IP Offload (TOE)
engines, iSCSI processing, RDMA, or encryption/decryption.
In this figure, the CPU on the adapter card is isolated from the
host CPU (not shown). The PEX 8508 non-transparent port
allows the two CPUs to be isolated but communicate with
each other through address translation that is integrated into
the PEX 8508. The upstream and downstream as well as the
non-transparent port of the PEX 8508 are fully configurable.
In this adapter, the CPU or other “intelligent” device with on-
chip processing capability—needs to be isolated from the rest
of the system to avoid memory mapping conflicts.
Figure 3. Aggregation Adapter Card
Figure 4. Intelligent Adapter
A low port/lane PCI Express switch can be very useful in a
print engine or similar type system controller in embedded
applications. Such designs require low port/lane counts and
low cost, yet the system throughput can be very high for
graphics oriented data. Figure 5 shows that the PEX 8508 is
used to transfer data from a scanner and other input devices to
the print engine CPU and back to the marking engine. Many
endpoint devices will be incorporating native PCI Express
support to allow the use of all five ports of the PEX 8508.
Complete power management support will reduce system
power consumption. With a small 19mm x 19mm footprint,
the controller board space can be minimized.
ATCA and XMC Mezzanine Card Applications
The PEX 8508 supports aggregation or fan-in/out as well as
peer-to-peer switching. Figure 6 shows each I/O Mezzanine
card with a PEX 8508 which can aggregate data to the main
baseboard or allow peer-to-peer switching between I/O
endpoints. Non transparency can isolate each of the I/O
Mezzanine cards from each other.
Office Automation Controller
Figure 5. Printer Controller Engine
Figure 6. XMC Mezzanine Card