IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 112 / 744

IDT Switch Partition and Port Configuration
PES32NT24xG2 User Manual 5 - 12 January 30, 2013
Notes
• Automatic speed change may be enabled by modifying the value of the Initial Link Speed
Change Control (ILSCC) bit in the PCI-to-PCI bridge function’s Phy Link Configuration 0
(PHYLCFG0) register.
– PCI Express requests that do not target functions 0, 1, 2 are completed with unsupported request
status by the port. The completion has a value of all zeroes in the function number field of the
completer ID.
NT Function Port
A port in NT function mode is a port composed of a non-transparent-bridge (NT) function.
– The NT function is function 0 of the port (i.e., type 0 header).
The port has the following behavior.
– The NT function behaves as described in Chapter 14.
– The LTSSM is operational and behaves as an upstream port.
• Since the link operates as an upstream port (i.e., downstream component), an automatic
speed change is not initiated when the link enters L0.
• The NT function does not implement the ILSCC bit. Still, although the PCI-to-PCI bridge func-
tion is not logically present in the port, proprietary registers within the function remain active.
Therefore, it is possible to program the ILSCC bit in a port that operates in NT function mode
by accessing the port’s PCI-to-PCI bridge function registers via the global address space
access registers (GASAADDR and GASADATA) located in the NT function’s configuration
space.
– Port output signals not associated with the NT function are kept in a negated state.
• All port output signals associated with downstream switch port operation are placed in a
negated state (i.e., hot-plug signals). The negated value of PxAIN, PxILOCKP, PxPEP, PxPIN,
and PxRSTN is determined as shown in Table 11.2.
– PCI Express requests that do not target function 0 are completed with unsupported request status
by the port. The completion has a value of all zeroes in the function number field of the completer
ID.
NT with DMA Function Port
A port in NT with DMA function mode is a multi-function upstream port composed of a non-transparent-
bridge (NT) function and a DMA function.
– The NT function is function 0 of the port (i.e., type 0 header).
– The DMA function is function 2 of the port (i.e., type 0 header).
The port has the following behavior.
– The NT function behaves as described in Chapter 14.
– The DMA function behaves as described in Chapter 15.
– The port follows the behavior for multi-function ports described in the PCI Express Base Specifi-
cation and in this document.
– The LTSSM is operational and behaves as an upstream port.
• Since the link operates as an upstream port (i.e., downstream component), an automatic
speed change is not initiated when the link enters L0.
• The NT and DMA functions do not implement the ILSCC bit. Still, although the PCI-to-PCI
bridge function is not logically present in the port, proprietary registers within this function
remain active. Therefore, it is possible to program the ILSCC bit in a port that operates in NT
function mode or NT with DMA function mode by accessing the port’s PCI-to-PCI bridge func-
tion registers via the global address space access registers (GASAADDR and GASADATA)
located in the NT or DMA function’s configuration space.
– Port output signals not associated with the NT function are kept in a negated state.
• All port output signals associated with downstream switch port operation are placed in a
negated state (i.e., hot-plug signals).