IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 268 / 744

IDT Non-Transparent Switch Operation
PES32NT24xG2 User Manual 14 - 20 January 30, 2013
Notes
Normally, devices with a PCI Express port capture the bus number associated with the port on reception
of type 0 configuration write requests that target the port. In system scenarios where there is no root
complex in the PCI Express hierarchy, the devices will not receive type 0 configuration write requests. As a
result, the default bus number (i.e., bus number 0) will be used by the devices, and ID-routing across the
hierarchy won’t be possible.
The switch contains a feature that allows software to explicitly configure the bus number associated with
a switch port that has an NT function. The programming is done by writing to the Bus (BUS) field in the
TLCNTCFG register located in the port’s configuration space. Programming of the port’s bus number is only
allowed when the port operates in NT function mode or NT with DMA function mode.
Figure 14.11 shows a system scenario where a PCI Express switch is used to connect several intelligent
devices. This system does not have a root complex, and communication among the intelligent devices is
desired. Each intelligent device uses a PES32NT24xG2 NT port to connect to the PCI Express switch. Prior
to initiating communication, the CPU located in the intelligent device programs the PES32NT24xG2 NT port
that faces the rootless PCI Express hierarchy with an appropriate requester ID (i.e., by writing to the BUS
field in the NT port’s TLCNTCFG register; this register can be accessed by the processor on the intelligent
device using switch’s global address space access registers).
Once the requester IDs for each intelligent device are programmed with unique values, traffic across the
rootless PCI Express switch routes normally.
Figure 14.11 Example of a Rootless PCI Express Hierarchy with Bus Number Reprogramming
Interrupts
The NT endpoint has six the following sources of interrupts.
– Message status
– Doorbell status
– Switch events
– Failover change initiated by failover capability associated with partition
– Failover change completed by failover capability associated with partition
– A temperature sensor alarm (see Chapter 18, Temperature Sensor).
NT
Endpoint
NT
Endpoint
R oot
Com plex
Sw itch
Intelligent D evice
N T
E ndpoint
N T
E ndpoint
S w itch
N T
Endpoint
N T
Endpoint
S w itch
Program m able
Requester ID
Port Port P ort
ID T
PC I Express
Sw itch
N o root com plex
connected to this
sw itch
M anager
S M Bus
PC Ie
Root
Com plex
Intelligent D evice
R oot
Com plex
Intelligent D evice