IDT PCI Express 89HPES32NT24xG2, User Manual, Page: 359 / 744

IDT Register Organization
PES32NT24xG2 User Manual 19 - 15 January 30, 2013
These registers are not directly accessible by PCI Express configuration request when a port is configured to operate in the following modes:
– Disabled
– Unattached
– Upstream switch port
– Upstream switch port with DMA function
– Downstream switch port
These registers are always accessible regardless of the port operating mode via the global address space access registers (i.e., GASAADDR and
GASADATA), via the SMBus slave interface, or via serial EEPROM. Restrictions apply when using the GASAADDR and GASADATA registers. Refer
to the definition of these registers for details. Note that the NT function allows mapping of its configuration space to memory space using the BAR 0
aperture. Thus, these configuration space registers may be accessed via memory read or writes. See section Mapping NT Configuration Space to
BAR 0 on page 14-4 for details.
Figure 19.3 shows the organization of the configuration space.