Datasheet 423
PCI-to-PCI Bridge Registers (D30:F0)
11.1.13 MEMBASE_LIMIT—Memory Base and Limit Register
(PCI-PCI—D30:F0)
Offset Address: 20h–23h Attribute: R/W
Default Value: 00000000h Size: 32 bits
This register defines the base and limit, aligned to a 1-MB boundary, of the non-
prefetchable memory area of the bridge. Accesses that are within the ranges specified
in this register will be sent to PCI if CMD.MSE is set. Accesses from PCI that are outside
the ranges specified will be accepted by the bridge if CMD.BME is set.
11.1.14 PREF_MEM_BASE_LIMIT—Prefetchable Memory Base
and Limit Register (PCI-PCI—D30:F0)
Offset Address: 24h–27h Attribute: R/W, RO
Default Value: 00010001h Size: 32-bit
Defines the base and limit, aligned to a 1-MB boundary, of the prefetchable memory
area of the bridge. Accesses that are within the ranges specified in this register will be
sent to PCI if CMD.MSE is set. Accesses from PCI that are outside the ranges specified
will be accepted by the bridge if CMD.BME is set.
Bit Description
31:20
Memory Limit (ML) — R/W. These bits are compared with bits 31:20 of the incoming
address to determine the upper 1-MB aligned value (exclusive) of the range. The
incoming address must be less than this value.
19:16 Reserved
15:4
Memory Base (MB) — R/W. These bits are compared with bits 31:20 of the incoming
address to determine the lower 1-MB aligned value (inclusive) of the range. The
incoming address must be greater than or equal to this value.
3:0 Reserved
Bit Description
31:20
Prefetchable Memory Limit (PML)
— R/W. These bits are compared with bits 31:20
of the incoming address to determine the upper 1-MB aligned value (exclusive) of the
range. The incoming address must be less than this value.
19:16 64-bit Indicator (I64L)
— RO. Indicates support for 64-bit addressing.
15:4
Prefetchable Memory Base (PMB) — R/W. These bits are compared with bits 31:20
of the incoming address to determine the lower 1-MB aligned value (inclusive) of the
range. The incoming address must be greater than or equal to this value.
3:0 64-bit Indicator (I64B)
— RO. Indicates support for 64-bit addressing.
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