User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 8: PCI Bus and HyperTransport Fabric Page
205
This is an optimization because the endian swap is several instructions compared to the single OR (and in
many cases all of the control registers need the swap so the base address of the control block can just be offset
once; or if all the control registers are mapped in a single TLB entry and the data accesses in another then the
virtual to physical mapping could set the Match Bits address bit for control and not for the data ranges).
The standard address is the Match Bytes since this makes memory order correct and thus causes unoptimized
(but endian aware) code to work correctly.
A
CCESSING
THE
S
I
B
YTE
FROM
PCI D
EVICES
The normal PCI Base Address Register (BAR) access scheme is used to accept accesses from the PCI bus
and map them to internal accesses. The PCI bus uses 32 bit addresses. To allow PCI masters to do transfers
to memory, other devices in the part and peer-to-peer transfers to devices on the HyperTransport a full 40 bit
address must be constructed. With the exception of expansion memory space and expansion HyperTransport
space the part places everything in the low 4G of the address space (physical address bits [39:32] are zero)
allowing a direct map from the 32 bit address on the PCI bus. In addition there is a map table that allows each
of sixteen 1 MB regions of PCI space to map to a full 40 bit address anywhere in the internal or HyperTransport
space.
The PCI controller has a type 0 (device) configuration header. This allows for up to 6 BARs, 5 are used when
the interface is in Host Mode and 3 are used when the interface is in Device Mode. In addition a PCI expansion
ROM may be accessed through its special BAR.
shows the BARs and the internal addresses that they map to. In Host Mode they default to the
values shown and are enabled following reset (if transparent access from PCI is all that is needed then no
changes are required by the configuration code). When the interface is run in Device Mode the BARs will be
setup by the host (using addresses in the host space). Note that the table shows the addresses. Since the
spaces are prefetchable the value in the PCI BAR register will have bit 2 set.
Table 123: PCI Base Address Register Use
Reg
Offset in
Config
Header
PCI
Size
Default PCI Base
Address in Host
Mode
PCI Base
Address in Device
Mode
Internal Base
Address
Internal Device
BAR0
+10
16M
6000_0000
(R/O)
xx00_0000
Table Lookup
Region controlled by map
table.
BAR1
+14
0
0000_0000
0000_0000
-
Reserved
BAR2
+18
4K
7000_0000
(R/O)
xxxx_x000
00_1002_1xxx
Mailbox CPU 0. Match
Bytes mode is used if the
system is configured Big
Endian.
BAR3
+1c
4K
7100_0000
R/O
xxxx_x000
00_1002_3xxx
Mailbox CPU 1. Match
Bytes mode is used if the
system is configured Big
Endian.
BAR4
+20
1G
0000_0000
(R/O)
Reserved
00_0000_0000
Memory below PCI space
(PCI a[29] indicates
endian policy).
BAR5
+24
2G
8000_0000
(R/O)
Reserved
00_8000_0000
Memory above PCI
space (PCI a[29]
indicates endian policy).
ROM
+30
64K
7300_0000
(R/O)
xxxx_0000
00_1FD0_xxxx
Expansion ROM. Match
Bytes mode is used if the
system is configured Big
Endian.
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