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
253
Table 153: HyperTransport Error Status Register - Offset 68 Bits [31:24]
Bits
Name
Default
Description
0
ProtoErr
R/C 1’b0
This bit will be set if a protocol error is detected on the incoming link.
Software may clear this bit by writing a 1 to it.
In some circumstances this bit will be set by a HyperTransport link reset.
1
OvfErr
R/C 1’b0
This bit will be set if the receive FIFO overflows.
Software may clear this bit by writing a 1 to it.
2
EocNxaErr
R/C 1’b0
This bit will be set if a Non Existent Address (NXA) error is returned to a request from
the incoming link because the End Of Chain bit (bit 6 in the link control register) is set.
Software may clear this bit by writing a 1 to it. This bit will also be set if a request is
rejected because the link has not been established (the InitDone bit is clear).
3
SrcTagErr
R/C 1’b0
This bit will be set if a response packet is received with a source id that does not
match any outstanding request.
Software may clear this bit by writing a 1 to it.
4
MapNxaError
R/C 1’b0
This bit will be set if a Non Existent Address (NXA) error is returned due to a mapping
problem with the request. There are two causes:
1) A packet is received that does not match one of the valid address ranges in
.
2) A packet is received that is decoded as having an address on the HyperTransport
link and with a zero source id. This indicates that the packet is a peer-to-peer
HyperTransport transaction, but it originated in the host bridge at the far end of the
link and has therefore not been accepted by any device on the link.
This bit is also set (but no error packet sent) if a response is received that has source
id of zero and did not come from this host.
Software may clear this bit by writing a 1 to it.
7:5
Reserved
R/O 3’b0
Reserved
Table 154: HyperTransport SRI Transmit Control Register - Offset 6C Bits [23:16]
Bits
Name
Default
Description
3:0
BufRelSpace
R/W
4’b0100
This field sets the minimum number of packets that will be sent between buffer
release NOP packets. If the link is idle buffer release packets are sent immediately.
If the link is busy buffer release messages are inserted into the packet stream with
this minimum spacing so that the bandwidth is not consumed with flow control
traffic.
7:4
Reserved
R/O 4’b0
Reserved
Table 155: HyperTransport SRI Data Buffer Allocation Register - Offset 6C Bits [15:0]
Bits
Name
Default
Description
1:0
NeedResp
R/W 2’b01
This register controls the allocation of the 8 HyperTransport receive data buffers
among the 3 virtual channels, to allow performance tuning.
The "Need" fields indicate the minimum allocation at all times to each channel,
minus one. That is, a value of 0 indicates a permanent minimum allocation of 1.
The total number of buffers "needed" must be less than or equal to 8 or the behavior
of the bridge is UNDEFINED. If the number of "needed" buffers is less than 8 the
allocator will dynamically allocate them to the three channels, subject to the limits
set in the "Want" fields.
The "Want" fields indicate how many buffers the allocator should try to have
released and outstanding to each channel at all times, minus 1.
In the default (reset) case, there are 2 buffers in each category.
Note that these counts must not be set to 2’b11 (i.e. 4 buffers) or the system may
behave in UNDEFINED ways.
3:2
NeedNpReq
R/W 2’b01
5:4
NeedPReq
R/W 2’b01
7:6
Reserved
R/O 2’b00
9:8
WantResp
R/W 2’b01
11:10
WantNpReq
R/W 2’b01
13:12
WantPReq
R/W 2’b01
15:14
Reserved
R/O 2’b00
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