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IDT Switch Partitions
Notes
PES48H12G2 User Manual
Refer to section Static Reconfiguration on page 6-15 for a sample partition and port configuration
sequence programmed via the serial EEPROM.
Partition State Change via Other Methods
When modifying the state of a partition via methods other than EEPROM loading (i.e., via PCI Express
configuration requests or using the SMBus slave), the following requirements and restrictions apply:
– Once a partition state change has been initiated, it must be allowed to complete (e.g., by polling
the SCI field) before a new partition state change is initiated on the same partition, before
changing the operating mode of ports in the partition, and before adding ports into the partition.
Violating this rule produces undefined results.
• The setting of the SCC bit indicates that all changes associated with the state change in the
entire device have completed (e.g., port operating mode changes).
– The state of a partition must not be modified at the same time that the operating mode of one or
more ports in the partition is being changed. Violating this rule produces undefined results.
– The state of a partition must not be modified at the same time that one or more ports are being
added into the partition. Violating this rule produces undefined results.
– When a partition is experiencing fundamental reset caused by the assertion of the partition funda-
mental reset signal (PARTxPERSTN), the following partition state changes will not complete (i.e.,
the SCC bit will not be set) until the PARTxPERSTN signal is de-asserted:
Disabled Active
Fundamental Reset Active
Switch Ports
A switch port is a logical entity that represents a PCIe link, stack logic (e.g., physical layer, data link
layer, etc.), and TLP queues (i.e., port's IFB and EFB) required to communicate on that link. All switch ports
are completely independent. The configuration or state of one switch port in no way affects the operation or
restricts the possible configuration of another port.
Switch Port Mode
A switch port may be configured to operate in one of the following modes.
– Disabled
– Unattached
– Upstream switch port
– Downstream switch port
A port in the disabled or unattached state is not associated with any switch partition (i.e., the port is
considered unattached).
A port in an operational mode is attached to the partition specified by the Switch Partition (SWPART)
field in the corresponding Switch Port x Control (SWPORTxCTL) register. The following switch port modes
are considered operational modes.
– Upstream switch port
– Downstream switch port
In general, the state of a port is determined by the Mode (MODE) field in the Switch Port Control
(SWPORTxCTL) register. The only exception is a port that is attached to a partition that is in the disabled
state. A disabled partition causes all attached ports to be in a disabled mode regardless of the MODE field
setting.
Disabled
A port that is disabled is considered unused and is placed in a low power state. For example, the port
does not generate power management messages, it does not generate INTx or MSI interrupts, and it not
generate error messages.
6 - 4
April 5, 2013
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