Functional Description

MPC Bus Address

2

8 0 8 0 1 2 3 4

0

 

 

15

16

 

 

 

 

 

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Decode is >= and <=

MSADDx Register

7 0 8 0 9 0 0 0

0

15

16

31

Figure 2-2. MPC-to-PCI Address Decoding

The Raven ASIC imposes no limits on how large an address space a map decoder can represent. There is a minimum of 64KB due to the resolution of the address compare logic.

For each map, there is an associated set of attributes. These attributes are used to enable read accesses, enable write accesses, enable write-posting, and define the PCI transfer characteristics.

Each map decoder also includes a programmable 16-bit address offset. The offset is added to the 16 most significant bits of the MPC address, and the result is used as the PCI address. This offset allows PCI devices to reside at any PCI address, independent of the MPC address map. An example of this appears in Figure 2-3.

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2-5

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Motorola MVME2300 Series manual MPC-to-PCI Address Decoding