Specifications

36 Programming Information HW400p/M Technical Reference - 1.0, March 6, 2002
5-2. Local PCI Address Space Map
The local PCI bus address space is arbited by the MPC8245, which provides
the IDSEL lines and performs the PCI configuration phase of the local PCI bus.
Firmware Unlike a standard PCI BIOS implementation, the MPC8245 firmware does not
use a dynamic address map. The firmware uses static mapping because it
knows of all possible PCI devices on the bus and their required window sizes.
This simplifies the on board software by allowing static addressing to be used.
Components on the installed PMC modules can be mapped within the 512MB
set aside for that purpose.
Masters There are four possible masters on the local PCI bus:
•MPC8245
• Am79C973 Ethernet controller
•PMC site
• Intel 21554 PCI-to-PCI Bridge
Master windows Each master has a master window onto the bus that allows it access to
specific resources. Table 5-2 shows the access regions for the individual
masters.
Location rules.
Two basic rules dictate the location of the main regions. First, no
master can access its own resources via the PCI bus; that is, a device’s
master window cannot overlap the resources it exposes to the PCI bus.
Second, the base address of a master window must be a multiple of the
window’s size. For example, the 2GB MPC8245 master window must start on
one of the two 2GB boundaries.
Host PCI bus address space.
The 21554 PCI-to-PCI Bridge can map up to 1GB of
primary PCI bus address space onto the local PCI bus. This space then falls
within the MPC8245 master window, allowing the MPC8245 access to the
host’s memory.
Table 5-2 Masters and window access regions
Master Window Access Region
MPC8245 All regions except its own memory and Configuration
Space Register (CSR) registers (KMEM and KCSR regions).
Ethernet controller The MPC8245’s memory, allowing it to do DMA transfers.
21554 Maps the MPC8245’s memory, or a portion thereof, and
CSR registers onto the hosts PCI bus to allow the host
system processor access to those memory areas.
PMC All regions except its own memory space.