User`s guide

4.2 21164 Address Mapping to PCI Space

Note

The window base addresses should be on NATURALLY ALIGNED

address boundaries, depending on the size of the window.

Figure 4–6 Addressing Diagram: PCI Target Window Compare

Peripheral Page Number

Offset

31 −1 20 19 13 12 0

PCI Address

31 −1 20

Compare Hit

PCI Base

PCI Mask

(Determines )

XXX

11100000000

MK−2306−10

When an address match occurs with a PCI target window, the EB164 translates

the 32-bit PCI address to a 34-bit processor byte address. The EB164 only

supports a 30-bit memory address. The translated address is generated in one

of two ways as determined by the scatter-gather (SG) bit of the window’s PCI

base register.

If the SG bit is cleared, the DMA address is direct mapped, and the translated

address is generated by concatenating bits from the matching window’s

translated base register with bits from the incoming PCI address. The PCI

mask register determines which bits of the translated base register and PCI

address are used to generate the translated address as shown in Table 4–13.

The unused bits of the translated base register must be cleared for proper

operation. Because system memory is located in the lower 1GB of the CPU

address space, address bits <39:33> are always 0. Address <32:5> is obtained

from the translated base register.

4–22 System Address Mapping