Datasheet
PCI Express Extended Configuration Space
98
March 5 2007 − June 2011SCPS154C
5.24 VC Resource Capability Register (VC1)
The VC resource capability register for VC1 provides information to software regarding the port and arbitration
schemes supported by the bridge. See Table 5−20 for a complete description of the register contents.
PCI Express extended register offset: 16Ch
Register type: Read-only
Default value: 077F 0011h
BIT NUMBER 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
RESET STATE 0 0 0 0 0 1 1 1 0 1 1 1 1 1 1 1
BIT NUMBER 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RESET STATE 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1
Table 5−20. VC Resource Capability Register (VC1) Description
BIT FIELD NAME ACCESS DESCRIPTION
31:24
PORT_ARB_
TBL_OFFSET
R
Port arbitration table offset. This read-only field returns the value 07h to indicate that the port
arbitration table for this VC begins 112 bytes from the top of the VC capability structure.
23 RSVD R Reserved. Returns 0b when read.
22:16
MAX_TIME_
SLOTS
R
Maximum time slots. The read-only field returns the value 7Fh to indicate that all 128 slots are
supported for time-based WRR.
15
REJECT_
SNOOP
R
Reject snoop transactions. This bit only has meaningful context for root ports and therefore returns
0b when read.
14
ADV_
SWITCHING
R
Advanced packet switching. This read-only bit returns the value 0b to indicate that the use of this
VC is not limited to AS traffic.
13:8 RSVD R Reserved. Returns 00 0000b when read.
7:0
PORT_
ARB_CAP
R
Port arbitration capability. This 8-bit encoded field indicates support for the various schemes that
are supported for port (secondary PCI device) arbitration. The field is encoded as follows:
Bit 0 = Hardware fixed arbitration (round-robin)
Bit 1 = WRR with 32 phases
Bit 2 = WRR with 64 phases
Bit 3 = WRR with 128 phases
Bit 4 = Time-based WRR with 128 phases
Bit 5 = WRR with 256 phases
Bit 6 = Reserved
Bit 7 = Reserved
The returned value of 11h indicates that hardware-fixed round-robin and time-based WRR with
128 phases are both supported.
Not Recommended for New Designs