Offsets, Upstream I/O or Memory 0 BAR

List of Registers

Table 37. Downstream I/O or Memory 1 and Upstream I/O or Memory 0 BAR

Offsets	Downstream I/O or Memory 1 BAR	Upstream I/O or Memory 0 BAR

Primary byte	1B:18h	5B:58h

Secondary byte	5B:58h	1B:18h

These registers define forwarding address ranges for downstream or upstream I/O or memory transactions. After reset, they are disabled and return all zeros when read.

This register can request a 64, 128, or 256 bytes I/O space. Hardware does not restrict larger I/O windows or 4 KB to 2 GB. To configure a space use serial preloading or program the Downstream I/O or Memory 1 Setup register or Upstream I/O or Memory 0 Setup register.

Access of the setup registers must be through the local processor before the Primary Lockout Reset Value bit is cleared.

Bit	Name	R/W	Description

			• When a 0, this BAR is disabled or memory space is requested
0	Space Indicator	R	memory space.
0	Space Indicator	R	• When a one (1), I/O space is requested.
			• When a one (1), I/O space is requested.
			• Reset value is 0

			• When all zeros (0s), I/O space is requested.
2:1	Type	R	• When non-zero, memory space is requested and the number
2:1	Type	R	equals the size and location of this address range.
			equals the size and location of this address range.
			• Reset value is 00b

			• When 0, requesting I/O or nonprefetchable memory.
3	Prefetchable	R	• When 1, requesting prefetchable memory space.
			• Reset value is 0

5:4	—	R	Returns zeros (0s).

			Indicate the size of the requested address range and set the base
			address of the range.
			The corresponding setup register determine the function of the
			corresponding bit in this register.
			• When a 0, the same bit in this register is a read-only bit and always
31:6	Base Address	R/W	return 0 when read.
31:6	Base Address	R/W	• When a one (1), the same bit in this register is writable and return

			the value last written when read.
			This BAR is disabled by writing a 0 to bit [31] of the setup register. The
			minimum size for an I/O address range is 64 bytes and for a memory
			range is 4 KB. The maximum size is 2 GB.
			• Reset value is This register is disabled (read only as 0).

21555 Non-Transparent PCI-to-PCI Bridge User Manual

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21555 specifications

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Intel 21555 user manual Downstream I/O or Memory 1 and Upstream I/O or Memory 0 BAR, Offsets

Models: 21555

Table 37. Downstream I/O or Memory 1 and Upstream I/O or Memory 0 BAR

Offsets

Upstream I/O or Memory 0 BAR

Bit

21555 specifications