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
243
In Host Mode the header should be configured by the local processor (in many cases the default values will be
reasonable and only the map table will need to be initialized), in Device Mode it will be configured by the
external host.
The map table allows control of what areas of the internal memory map are accessible to an external PCI
master. Therefore it is protected and can only be used with configuration accesses from the ZBbus side of the
bridge. Configuration accesses to the map table registers will be accepted from the PCI bus, but the writes will
be ignored and reads will return UNPREDICTABLE values. When the interface is run in Device Mode, the
external master will always see the BAR0 region as a 16 MByte space that needs an address allocation,
software running on the device should configure the map table to allow access to appropriate internal
resources. The peer-to-peer mappings in the map register give the part some of the characteristics of a non-
transparent PCI to HyperTransport bridge.
The SubSysSet register can only be written from the ZBbus side of the bridge. It is used to provide a value in
the SubSystem Device and Vendor Id registers seen by external configuration reads. In Device Mode software
on the device should write the SubSysSet register with a value that identifies the manufacturer of the option
card and its part number. This write must be done early in initialization, before the host needs to read the value.
On interface revision 3 and later the Device/Vendor Id and the Class code that will be read by the external host
can also be changed by using the VendorIdSet and ClassRevSet registers.
7
dis_memrd_be
1'b0
This bit should be zero for normal operation. If set the byte enables will always
be all set for read transactions.
8
prefetch_en
R/W 1’b0 Interface revision 3 or greater: this bit may be set to enable read prefetching to
improve performance of block reads from the ZBbus to the PCI.
9
prefetch_sz
R/W 1’b0 Interface revision 3 or greater: if this bit is 0 two cachelines are prefetched when
the prefetch_en bit is set, if it is 1 then 4 cachelines are prefetched.
31:10
notimp
22b'x
Not Implemented.
Table 138: PCI Adaptive Extend Register - Offset 98 Bits [31:0]
(Cont.)
Bits
Name
Default
Description
Table 139: PCI Bypass Control Register - RevId >= 3 Offset A8 Bits [31:0]
Bits
Name
Default
Description
11:0
num_pior_byp
R/W
12’hFFF
A ZBbus or HT-to-PCI initiated read will be retried a total of num_pior_byp
multiplied by the retry_timeout (in the Timeout register). Each retry_timeout there
is a chance for one write to bypass the read (this is a workaround for older devices
that did not correctly implement the PCI ordering rules).
31:12
notimp
20b'x
Not Implemented.
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