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
246
Section 8: PCI Bus and HyperTransport Fabric
Document
1250_1125-UM100CB-R
70-C4
Reserved R/O Unpredictable
Reserved
C8
TxBufCountMax (See
R/W 00FFFFFF
Transmit buffer control register.
CC-D8
Reserved R/O Unpredictable
Reserved
DC
DiagRxCrcE (See
R/O xxxxxxxx
Expected CRC (diagnostic register).
E0-EC
Reserved R/O Unpredictable
Reserved
F0
DiagRxCrcR (See
)
R/O xxxxxxxx
Received CRC (diagnostic register).
F4-FC
Reserved R/O Unpredictable
Reserved
Table 140: HyperTransport Configuration Header (Type 1)
(Cont.)
Offset
Register Bits
Description
31
24
23
16
15
8
7
0
Table 141: HyperTransport Bridge Command Register - Offset 4 Bits [15:0]
Bits
Name
Default
Description
0
IoSpaceEn
R/O 1’b1
I/O Space Enable. This bit is always set. The HyperTransport bridge always forwards
I/O space transactions that originate on the ZBbus and match the bridge I/O range.
Peer-to-Peer I/O is not supported between PCI and HyperTransport.
1
MemSpaceEn
R/O 1’b1
Memory Space Enable. This bit is always set. The HyperTransport bridge always
forwards memory space transactions that originate on the ZBbus and match the
bridge memory range. Peer-to-Peer transfers from the PCI bus will always be
accepted by the HyperTransport bridge, but they can be disabled in the PCI bridge
by clearing the ptp_en bit in the PCI Feature Control Register (see
).
2
MasterEn
R/W 1’b0
Primary Bus (i.e. ZBbus) Master Enable. This bit controls acceptance of requests
from the HyperTransport fabric. If a request has unitid=0 and contains an address
that should be sent back on the HyperTransport fabric (a peer-to-peer operation) it
must have come the whole length of the fabric from another host bridge and it will
always be responded to with an NXA error.
0: Accept only Configuration Cycles and requests that must be sent back out on the
HyperTransport fabric. All other posted requests are dropped and non-posted
requests return an NXA error.
1: Accept all requests that match an address range in this part.
3
SpecCycEn
R/O 1’b0
These bits apply to PCI bridges only. For a HyperTransport bridge they are read only
and always return zero.
4
MemWrInvEn
R/O 1’b0
5
VgaPalSnpEn
R/O 1’b0
6
ParErrResp
R/O 1’b0
7
WaitCycCtrl
R/O 1’b0
8
SerrEn
R/W 1’b0
SERR enable. This controls the SERR on the primary interface. Since the ZBbus has
no equivalent of SERR the setting of this bit is ignored.
9
FastB2BEn
R/O 1’b0
These bits apply to PCI bridges only. For a HyperTransport bridge they are read only
and always return zero.
15:10
reserved
R/O 6’b0
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