Freescale Semiconductor MPC8260 - Manual (Page 332)

PCI Bridge
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
9-26 Freescale Semiconductor
9.10.2.2 PCI Outbound Translation
Outbound address translation is provided to allow the outbound transactions to access any address over the
PCI memory or I/O space. Translation window’s base addresses are defined in the PCI outbound base
address registers (refer to
Section 9.11.1.4, “PCI Outbound Base Address Registers (POBARx)” ).
Transactions to these address ranges are issued on the PCI bus with a translated address. The translation
addresses are defined in the associated PCI outbound translation address registers (POTARs). Outbound
addresses that fall outside the outbound windows are forwarded to the PCI bus without modification.
Figure 9-16 shows an example translation window for outbound memory accesses.
Figure 9-16. Outbound PCI Memory Address Translation
The three sets of outbound translation registers allow three simultaneous translation windows. Software
can move and adjust the host memory window translations and sizes during run-time. This allows software
to access host memory or to address alternate memory space on the fly, but be sure that the PCI outbound
translation windows do not overlap. Also note that the PCI outbound translation windows should not
overlap with the PCI bridge internal register space defined by the PIMMR.
9.10.3 SIU Registers
PCI utilizes fields in general SIU registers (SIUMCR, TESCR1, TESCR2, and L-TESCR1). There are also
two pairs of PCI-specific registers that detect accesses from the 60x bus side to the PCI bridge (other than
PCI internal registers accesses). Refer to
Section 4.3.4, “PCI Control Registers.”
60x bus view PCI memory view
0 0
4G 4G
Local memory
PCI memory
System memory
PCI memory
Outbound address
translation
PCI outbound
translation
address
Outbound memory
window
System memory
window
Transactions outside
the window forwarded
without modification
Outbound
memory
window size
PCI outbound
base
address
Outbound
memory
window size