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21555 Non-Transparent PCI-to-PCI Bridge User Manual 137
List of Registers
Table 42. Downstream Memory 0, 2, 3, and Upstream Memory 1 Translated Base Register
These registers contain the translated base addresses for their respective downstream and upstream BARs.
The base address of the transaction on the initiator bus is replaced by the base address contained in these
registers
These registers are also mapped in the 21555 I/O and memory CSR space.
Bit Name R/W Description
11:0 Reserved R Reserved. Returns 0 when read.
31:12 XLAT_BASE R/W
Contains the translated base address for downstream or upstream
transactions whose initiator bus addresses fall into one of the
following address ranges:
• Downstream Memory 0 (above low 4K boundary)
• Downstream Memory 2
• Downstream Memory 3
• Upstream Memory 1
The number of bits that are used for the translated base is
determined by the setup register corresponding to that base
address and also matches the number of writable bits in the
corresponding BAR.
The remaining bits can be written but are ignored when performing
address translation. When a memory transaction is initiated by the
21555 on the target bus, the original base address is replaced with
the value contained in this register.
Offsets
Downstream
Memory 0
Translated Base
Downstream
Memory 2
Translated Base
Downstream
Memory 3
Translated Base
Upstream
Memory 1
Translated Base
Primary byte 97:94h 9F:9Ch A3:A0h AB:A8h
Secondary byte 97:94h 9F:9Ch A3:A0h AB:A8h
CSR byte 06B:068h 073:070h 077:074h 07F:07Ch