BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
248
Section 8: PCI Bus and HyperTransport Fabric
Document
1250_1125-UM100CB-R
Table 144: HyperTransport Bridge Control Register - Offset 3C Bits [31:16]
Bits
Name
Default
Description
0
ParErrRespEn
R/O 1’b0
This bit applies to PCI bridges only. For a HyperTransport bridge it is read only
and always returns a zero.
1
SerrEn
R/W 1’b0
This bit must be set to enable detection of Sync flooding on the HyperTransport
link.
2
IsaEn
R/O 1’b0
This bit is always zero. The HyperTransport bridge does not support modified ISA
address forwarding.
3
VgaEn
R/W 1’b0
This bit controls the routing of VGA address accesses in the compatibility spaces
(
0A_0000
-
0B_FFFF
in memory space and
X3B0
-
X3BB
and
X3C0
-
X3DF
in I/O
space). If this bit is clear these addresses are sent to the PCI interface and if set
they are sent (without the COMPAT bit set) to the HyperTransport fabric.
4
Reserved
R/O 1’b0
Reserved
5
MstrAbortMode
R/W 1’b0
Error response behavior. This bit determines the way errors are forwarded through
the HyperTransport bridge.
If this bit is set:
Any ZBbus error causes a HyperTransport Error response with the NXA bit
clear.
Any HyperTransport error causes a ZBbus Bus Error.
If this bit is clear:
Any ZBbus Bus Error or Fatal Error causes a valid HyperTransport response.
Any other ZBbus Error causes a HyperTransport error response with the
NXA bit clear.
Any HyperTransport error with the NXA bit set causes a ZBbus response
with valid data that is all ones.
Any HyperTransport error with the NXA bit clear causes a ZBbus Bus Error
response.
6
SecBusReset
R/W
1’b0
If this bit is set the LDT_RESET_L signal is asserted.
If the WarmReset bit in the HyperTransport host interface command register is clear,
the LDT_PWROK signal is deasserted to cause a cold reset.
When this bit is set, clearing it will bring the fabric out of reset.
7
FastB2BEn
R/O 1’b0
These bits apply to PCI bridges only. For a HyperTransport bridge they are read only
and always return zero.
8
PriDiscard
R/O 1’b0
9
SecDiscard
R/O 1’b0
10
DiscardStat
R/O 1’b0
11
DiscardSerrEn
R/O 1’b0
15:12
reserved
R/O 4’b0
Reserved
Table 145: HyperTransport Command Register - Offset 40 Bits [31:16]
Bits
Name
Default
Description
0
WarmReset
R/W 1’b1
If this bit is set then a warm reset of the fabric is done when the SecBusReset bit is
set in the Bridge Control Register. If this bit is clear a cold reset is done.
Changing the state of this bit when the SecBusReset bit is asserted results in
UNDEFINED behavior.
1
DoubleEnded
R/W 1’b0
This bit is set by the master host bridge on other side of the chain to indicate that the
slave host bridge is successfully configured on a double ended link. This bit is just
used by software, it has no affect on hardware.
6:2
Reserved
RevID>=3
DevNum
R/O 5’b0
R/W 5’b0
On interface RevID 1 and 2 this field is reserved.
On interface with RevId 3 and greater this field is used to set the Unit ID the part will
use if the ActAsSlave bit is set. The default is restored on a cold reset.