Freescale Semiconductor MPC8260 - Manual (Page 350)

PCI Bridge
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
9-44 Freescale Semiconductor
Figure 9-31. PCI Inbound Comparison Mask Registers (PICMR x)
Table 9-18. describes PICMRx.
31 30 29 28 20 19 16
Field EN
NO_
SNOOP_
EN
PRE — CM
Reset 0000_0000_0000_0000
R/W R/W
Addr 0x108FA (PICMR0); 0x108E2 (PICMR1)
15 0
Field CM
Reset 0000_0000_0000_0000
R/W R/W
Addr 0x108F8 (PICMR0); 0x108E0 (PICMR1)
Table 9-18. PICMR x Field Descriptions
Bits Name Description
31 Enable Setting this bit enables address translation
30 NO_SNOOP_EN Controls whether the PCI bridge generates snoop transactions on the 60x bus for
PCI-to-60x memory transactions which hit in this address translation window.
Disabling snooping is a performance enhancement for systems that do not need to
maintain coherency on system memory accesses by PCI.
0 Snooping is enabled.
1 Snooping is disabled.
29 Prefetchable Indicates whether the address space is prefetchable so that streaming can occur.
0 not prefetchable
1 prefetchable
28–20 — Reserved, should be cleared.
19–0 Comparison Mask Indicates the size of the space to be translated. The value in the register represents
which of the most significant address bits to compare for a window match.
Non-contiguous comparison mask bits cause unpredictable behavior.
Examples:
PICMR = 0b0xxx_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx_xxxx
Inbound window is disabled.
PICMR = 0b1xxx_xxxx_xxxx_1111_1111_1111_1111_1111
The mask is 20 bits (physical address bits 31-12) which corresponds to a 4Kbyte
window size. This is the smallest window size allowed.
PICMR = 0b1xxx_xxxx_xxxx_1111_1111_1111_0000_0000
The mask is 12 bits (physical address bits 31-20) which corresponds to a 1Mbyte
window size.