Downstream I/O Or Memory 1 And Upstream I/O Or Memory 0 Bar - Intel 21555 User Manual

Table 37. Downstream I/O or Memory 1 and Upstream I/O or Memory 0 BAR
Offsets
Primary byte
Secondary byte
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
0 Space Indicator
2:1 Type
3 Prefetchable
5:4 —
31:6 Base Address
21555 Non-Transparent PCI-to-PCI Bridge User Manual
Downstream I/O or Memory 1 BAR
1B:18h
5B:58h
R/W Description
• When a 0, this BAR is disabled or memory space is requested
memory space.
R
• When a one (1), I/O space is requested.
• Reset value is 0
• When all zeros (0s), I/O space is requested.
-
• When non zero, memory space is requested and the number
R
equals the size and location of this address range.
• Reset value is 00b
• When 0, requesting I/O or nonprefetchable memory.
R • When 1, requesting prefetchable memory space.
• Reset value is 0
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
return 0 when read.
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).
List of Registers
Upstream I/O or Memory 0 BAR
5B:58h
1B:18h
-
only bit and always
133