Datasheet

4−9
4.15 PCI Bus Number Register
This register is programmed by the host system to indicate the bus number of the PCI bus to which the PCI1520 is
connected. The PCI1520 uses this register in conjunction with the CardBus bus number and subordinate bus number
registers to determine when to forward PCI configuration cycles to its secondary buses.
Bit 7 6 5 4 3 2 1 0
Name PCI bus number
Type RW RW RW RW RW RW RW RW
Default 0 0 0 0 0 0 0 0
Register: PCI bus number
Offset: 18h (functions 0, 1)
Type: Read/Write
Default: 00h
4.16 CardBus Bus Number Register
This register is programmed by the host system to indicate the bus number of the CardBus bus to which the PCI1520
is connected. The PCI1520 uses this register in conjunction with the PCI bus number and subordinate bus number
registers to determine when to forward PCI configuration cycles to its secondary buses. This register is separate for
each PCI1520 controller function.
Bit 7 6 5 4 3 2 1 0
Name CardBus bus number
Type RW RW RW RW RW RW RW RW
Default 0 0 0 0 0 0 0 0
Register: CardBus bus number
Offset: 19h
Type: Read/Write
Default: 00h
4.17 Subordinate Bus Number Register
This register is programmed by the host system to indicate the highest-numbered bus below the CardBus bus. The
PCI1520 uses this register in conjunction with the PCI bus number and CardBus bus number registers to determine
when to forward PCI configuration cycles to its secondary buses. This register is separate for each CardBus controller
function.
Bit 7 6 5 4 3 2 1 0
Name Subordinate bus number
Type RW RW RW RW RW RW RW RW
Default 0 0 0 0 0 0 0 0
Register: Subordinate bus number
Offset: 1Ah
Type: Read/Write
Default: 00h