Information

System Configuration

MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1

Freescale Semiconductor 5-3

5.1.1 Address Translation and Mapping

In addition to any address translation performed by the e300 core MMU, three distinct types of translation

and mapping operations are performed on transactions at the integrated device level. These are as follows:

• Mapping a local address to a target interface

• Translating the local 32-bit address to an external address space

• Translating external addresses to the local 32-bit address space

The local access windows perform target mapping for transactions within the local address space. The

local access windows do not perform any address translation.

Outbound windows perform the mapping from the local 32-bit address space to the address space of the

PCI Express interface, which may be much larger than the local space.

Inbound windows perform address translation from the external address spaces of the PCI Express

interface to the local address space.

The target mappings created by an inbound window must be consistent with those of the local access

windows. That is, if an inbound window maps a transaction to a given local address, a valid local access

window for that address must be set independently.

All of the configuration registers that define mapping of local access windows follow the same register

format. Table 5-3 summarizes the general format of these window definitions.

Windows must be a power-of-two size. To perform a mapping function, the address of the transaction is

compared with the base address register of each window. The number of bits used in the comparison is

dictated by each window’s size attribute. When an address hits within a window, the transaction is directed

to the appropriate target.

5.1.2 Window into Configuration Space

The internal memory map registers’ base address register (IMMRBAR) defines a window that is used to

access all memory-mapped configuration, control, and status registers, referred to as internal memory map

registers or IMMR. This window is always enabled with a fixed size of 1 Mbyte, and no other attributes

are attached so there is no associated size/attribute register. This window always takes precedence over all

local access windows. The IMMRBAR always come out of reset with a default base address value of

Table 5-3. Format of Window Definitions

Base address High-order address bits defining location of the window in the initial address space

Window size/attributes Window enable, window size

An exception is the IMMR window, which is always enabled and has a fixed 1-Mbyte size.