Address Maps; Address Map B - Motorola MPC8240 User Manual

Chapter 3

Address Maps

The MPC8240 in PCI host mode supports two address mapping configurations designated
as address map A, and address map B. The address map is selected at reset by the MAA0
configuration pin. The address map selected at reset is stored as the initial value of the
PICR1[ADDRESS_MAP] bit. If the MPC8240 is configured as a PCI host and the address
map configuration pin is pulled low, the MPC8240 uses address map A. If the MPC8240 is
configured as a PCI host and the address map configuration pin is pulled high, the
MPC8240 uses address map B.
If the MPC8240 is configured as a PCI agent, it must be configured to use address map B.
In agent mode, the MPC8240 offers address translation capability to allow address
remapping for inbound and outbound PCI memory transactions. Translation allows a
certain address space to map to a window of physical memory.
The MAA1 reset configuration pin selects whether the MPC8240 is operating as a PCI host
or agent. For more information on the reset configuration signals, see Section 2.4,
"Configuration Signals Sampled at Reset."
Address map A conforms to the now-obsolete PowerPC reference platform (PReP)
specification. It is strongly recommended that new designs use map B because map A may
not be supported in future devices. For this reason, address map A is not described in this
chapter; instead, it is described in Appendix A, "Address Map A."
Address map B conforms to the PowerPC microprocessor common hardware reference
platform (CHRP). When the MPC8240 is configured as a PCI agent, only map B is
supported. This chapter describes map B.
The MPC8240 also has a block of local memory and PCI memory space that is allocated to
the control and status registers for several embedded features. This block is called the
embedded utilities memory block (EUMB). The EUMB and its offsets are also described
in this chapter.

3.1 Address Map B

The address space of map B is divided into four areas—local memory, PCI memory, PCI
I/O, and system ROM space. Throughout this chapter, the term local memory is used to
mean that (S)DRAM is directly controlled by the MPC8240 memory controller.
Chapter 3. Address Maps 3-1