Datasheet

PCI Express Extended Configuration Space
99
March 5 2007 − June 2011 SCPS154C
5.25 VC Resource Control Register (VC1)
The VC resource control register for VC1 allows software to control the second VC and associated port and
arbitration schemes supported by the bridge. See Table 5−21 for a complete description of the register
contents.
PCI Express extended register offset: 170h
Register type: Read-only, Read/Write
Default value: 0100 0000h
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 1 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 0 0 0 0 0 0 0 0 0 0 0 0
Table 5−21. VC Resource Control Register (VC1) Description
BIT FIELD NAME ACCESS DESCRIPTION
31 VC_EN RW
VC enable. This bit is used by software to enable this VC resource. Writing a 1b to this bit causes
the bridge to begin VC negotiation and set bit 1 (VC_PENDING) in the VC resource status register
for this VC (offset 176h, see Section 5.26). The default value for this bit is 0b.
30:27 RSVD R Reserved. Returns 0h when read.
26:24 VC_ID RW
Virtual channel ID. This field allows software to assign a VC ID to this VC resource. Valid values
range from 001b to 111b, because the value 000b is hardware-fixed to VC0 within the device. The
default value for this field is 001b.
23:20 RSVD R Reserved. Returns 0h when read.
19:17
PORT_ARB
_SELECT
RW
Port arbitration select. This read/write field allows software to define the mechanism used for port
arbitration by the bridge on this VC. The value written to this field indicates the bit position within
bits 7:0 (PORT_ARB_CAP) in the VC resource capability register for this VC (offset 16Ch, see
Section 5.24) that corresponds to the selected arbitration scheme. Values that may be written to
this field include:
000 = Hardware-fixed round-robin (default)
100 = Time-based WRR with 128 phases
All other values are reserved for arbitrations schemes that are not supported by the bridge.
16
LOAD_PORT
_TABLE
RW
Load port arbitration table. When software writes a 1b to this bit, the bridge applies the values
written in the port arbitration table for this VC within the extended configuration space to the actual
port arbitration tables used by the device for arbitration on this VC. This bit always returns 0b when
read.
15:8 RSVD R Reserved. Returns 00h when read.
7:0 TC_VC_MAP RW
TC/VC map. This field indicates all of the traffic classes that are mapped to this VC. A 1b in any bit
position indicates that the corresponding traffic class is enabled for this VC. A 0b indicates that the
corresponding traffic class is mapped to a different VC. The following table is used:
Bit 0 = Traffic class 0 (This bit is read only and returns a value of 0b)
Bit 1 = Traffic class 1
Bit 2 = Traffic class 2
Bit 3 = Traffic class 3
Bit 4 = Traffic class 4
Bit 5 = Traffic class 5
Bit 6 = Traffic class 6
Bit 7 = Traffic class 7
The default value of 00h indicates that none of the eight traffic classes are initially mapped to this
VC.
Not Recommended for New Designs