Datasheet
PCI Express Extended Configuration Space
92
March 5 2007 − June 2011SCPS154C
5.16 Next Capability Offset/Capability Version Register
This read-only register returns the value 000h to indicate that this extended capability block represents the
end of the linked list of extended capability structures. The four least significant bits identify the revision of the
current capability block as 1h.
PCI Express extended register offset: 152h
Register type: Read-only
Default value: 0001h
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 1
5.17 Port VC Capability Register 1
The first port VC capability register provides information to software regarding the VC capabilities support by
the bridge. See Table 5−13 for a complete description of the register contents.
PCI Express extended register offset: 154h
Register type: Read-only
Default value: 0000 08X1h
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 0 0 0 0 0 0 0 0 0 0 0
BIT NUMBER 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RESET STATE 0 0 0 0 1 0 0 0 0 0 0 x 0 0 0 1
Table 5−13. Port VC Capability Register 1 Description
BIT FIELD NAME ACCESS DESCRIPTION
31:12 RSVD R Reserved. Returns 00000h when read.
11:10 PORT_TABLE_SIZE R
Port arbitration table entry size. This read-only field returns a value of 10b to indicate
that the field size within the port arbitration table is four bits. This is necessary to allow
as many as six secondary PCI bus masters.
9:8 REF_CLK R
Reference clock. This read-only field returns a value of 00b to indicate than an internal
100-ns timer is used for time-based, WRR port arbitration.
7 RSVD R Reserved. Returns 0b when read.
6:4 LOW_PRIORITY_COUNT RU
Low priority extended VC count. When bit 25 (STRICT_PRIORITY_EN) in the general
control register (offset D4h, see Section 4.65) is 0b, the default
LOW_PRIORITY_COUNT is 001b. When STRICT_PRIORITY_EN is 1b, the default
LOW_PRIORITY_COUNT is 000b. When STRICT_PRIORITY_EN is set, strict priority
VC arbitration is used and the extended VC always receives priority over VC0 at the
PCI Express port.
3 RSVD R Reserved. Returns 0b when read.
2:0 EXT_VC_COUNT R
Extended VC count. This read-only field returns a value of 001b to indicate support for
one extended VC.
Not Recommended for New Designs