Datasheet
PCI Express Extended Configuration Space
100
March 5 2007 − June 2011SCPS154C
5.26 VC Resource Status Register (VC1)
The VC resource status register allows software to monitor the status of the port arbitration table for this VC.
See Table 5−22 for a complete description of the register contents.
PCI Express extended register offset: 176h
Register type: Read-only
Default value: 0000h
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 0 0 0 0 0
Table 5−22. VC Resource Status Register (VC1) Description
BIT FIELD NAME ACCESS DESCRIPTION
15:2 RSVD R Reserved. Returns 00 0000 0000 0000b when read.
1 VC_PENDING RU
VC negotiation pending. This bit is asserted when VC negotiation is in progress following a
request by software to enable the second VC.
0
PORT_TABLE
_STATUS
RU
Port arbitration table status. This bit is automatically set by hardware when any modification is
made to the port arbitration table entries for this VC within the extended configuration space.
This bit is cleared by hardware after software has requested a port arbitration table refresh and
the refresh has been completed.
5.27 VC Arbitration Table
The VC arbitration table is provided to allow software to define round-robin weighting for traffic targeting the
PCI Express port. The table is divided into 32 phases. See Table 5−24 for a complete description of the register
contents.
PCI Express extended register offset: 180h – 18Ch
Register type: Read-only, Read/Write
Default value: 0000 0000h
Table 5−23. VC Arbitration Table
REGISTER FORMAT OFFSET
Phase 7 Phase 6 Phase 5 Phase 4 Phase 3 Phase 2 Phase 1 Phase 0 180h
Phase 15 Phase 14 Phase 13 Phase 12 Phase 11 Phase 10 Phase 9 Phase 8 184h
Phase 23 Phase 22 Phase 21 Phase 20 Phase 19 Phase 18 Phase 17 Phase 16 188h
Phase 31 Phase 30 Phase 29 Phase 28 Phase 27 Phase 26 Phase 25 Phase 24 18Ch
Each phase consists of a four-bit field as indicated below.
BIT NUMBER 3 2 1 0
RESET STATE 0 0 0 0
Table 5−24. VC Arbitration Table Entry Description
BIT FIELD NAME ACCESS DESCRIPTION
3 RSVD R Reserved. Returns 0b when read.
2:0 VC_ARB_ID RW
Virtual channel ID. This 3-bit field is used by software to identify the VC ID that must be allocated to
this slot of arbitration bandwidth depending upon the VC arbitration scheme enabled. The default
value for this field is 000b.
Not Recommended for New Designs