Specification Sheet

Datasheet, Volume 2 of 2 149
DMIBAR Registers
6.12 DMI VCm Resource Control (DMIVCMRCTL)—
Offset 38h
Access Method
Default: 7000180h
Type: MEM
(Size: 32 bits)
Offset: [B:0, D:0, F:0] + 38h
3
1
2
8
2
4
2
0
1
6
1
2
8 4 0
0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0
VCMEN
RSVD
VCID
RSVD
FC_FSM_STATE
TCVCMMAP
Bit
Range
Default &
Access
Field Name (ID): Description
31
0h
RW
VCMEN: Virtual Channel enable:
0: Virtual Channel is disabled.
1: Virtual Channel is enabled. See exceptions below.
Software should use the VC Negotiation Pending bit to check whether the VC
negotiation is complete. When VC Negotiation Pending bit is cleared, a 1 read from this
VC Enable bit indicates that the VC is enabled (Flow Control Initialization is completed
for the PCI Express port). A 0 read from this bit indicates that the Virtual Channel is
currently disabled.
BIOS Requirement:
1. To enable a Virtual Channel, the VC Enable bits for that Virtual Channel should be
set in both Components on a Link.
2. To disable a Virtual Channel, the VC Enable bits for that Virtual Channel should be
cleared in both Components on a Link.
3. Software should ensure that no traffic is using a Virtual Channel at the time it is
disabled.
4. Software should fully disable a Virtual Channel in both Components on a Link
before re-enabling the Virtual Channel.
30:27
0h
RO
Reserved (RSVD): Reserved.
26:24
7h
RW
VCID: Virtual Channel ID: Assigns a VC ID to the VC resource. Assigned value should
be non-zero. This field can not be modified when the VC is already enabled.
23:13
0h
RO
Reserved (RSVD): Reserved.
12:8
1h
ROV
FC_FSM_STATE: This register is for Save Restore to restore the FC fsm
7:0
80h
RO
TCVCMMAP: Traffic Class/Virtual Channel Map: Indicates the TCs (Traffic Classes)
that are mapped to the VC resource. Bit locations within this field correspond to TC
values.
For example, when bit 7 is set in this field, TC7 is mapped to this VC resource. When
more than one bit in this field is set, it indicates that multiple TCs are mapped to the
VC resource. In order to remove one or more TCs from the TC/VC Map of an enabled
VC, software should ensure that no new or outstanding transactions with the TC labels
are targeted at the given Link.