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Figure A–17 PCI DMA Addressing Example
21164 System
8KB
Page
21164 Memory
Space (8GB)
Figure A–18 shows the PCI window logic. The comparison logic associated with
ad<63:32> is only used for DAC
window base register for window 3. This logic is only applicable to window 3. The
remaining windows only recognize 32-bit PCI addresses (that is, SAC
For a hit to occur in a DAC address, ad<63:40> must be zero, ad<39:32> must
match the window DAC base register, and ad<31:20> must also have a compare hit.
This scheme allows a naturally aligned, 1MB–4GB PCI window to be placed any-
where in the first 1TB of a 64-bit PCI address. When an address match occurs with a
PCI target window, the 21174 translates the 32-bit PCI address to addr_h<33:0>.
9
Dual-address cycle (DAC) — only issued if <63:32> are nonzero for a 64-bit address.
10
Single-address cycle (SAC) — all 32-bit addresses. A PCI device must use SAC if
<63:32> equals 0.
22 January 1998 – Subject To Change
Scatter-Gather
Map
PCI Memory
Space (4GB)
9
mode; and only if enabled by a bit in the
PCI to Physical Memory Address
PCI Device's DMA
Memory Space
PCI
Device 0
Device 1
System Address Space
PCI
PCI
Device 2
LJ-05402.AI4
10
cycles).
A–35
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