XIO2000AI datasheet(126/159 Pages) TAOS

126 / 159 page

PCI Express Extended Configuration Space

116

April 2007 Revised October 2008

SCPS155C

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

Read-only

Default value:

0000h

BIT NUMBER

RESET STATE

Table 5−22. VC Resource Status Register (VC1) Description

BIT

FIELD NAME

ACCESS

DESCRIPTION

15:2

RSVD

Reserved. Returns 00 0000 0000 0000b when read.

VC_PENDING

VC negotiation pending. This bit is asserted when VC negotiation is in progress following a

request by software to enable the second VC.

PORT_TABLE

_STATUS

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

Read-only, Read/Write

Default value:

0000 0000h

Table 5−23. VC Arbitration Table

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

RESET STATE

Table 5−24. VC Arbitration Table Entry Description

BIT

FIELD NAME

ACCESS

DESCRIPTION

RSVD

Reserved. Returns 0b when read.

2:0

VC_ARB_ID

Virtual channel ID. This 3-bit field is used by software to identify the VC ID that must be allocated

this slot of arbitration bandwidth depending upon the VC arbitration scheme enabled. The default

value for this field is 000b.

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