Datasheet

Datasheet, Volume 2 113
Processor Configuration Registers
2.9.5 EPVC1RCTL—EP VC 1 Resource Control Register
This register controls the resources associated with PCI Express Virtual Channel 1.
B B/D/F/Type: 0/0/0/PXPEPBAR
Address Offset: 20–23h
Reset Value: 0100_0000h
Access: RW, RO
Bit Attr
Reset
Value
Description
31 RW 0b
VC1 Enable (VC1E)
This bit will be ignored by the hardware. The bit is RW for specification
compliance, but writing to it will result in no behavior change in the hardware
(other than the bit value reflecting the written value).
0 = Virtual Channel is disabled.
1 = Virtual Channel is enabled.
See exceptions in notes below.
Software must 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.
Notes:
1. To enable a Virtual Channel, the VC Enable bits for that Virtual Channel
must be set in both Components on a Link.
2. To disable a Virtual Channel, the VC Enable bits for that Virtual Channel
must be cleared in both Components on a Link.
3. Software must ensure that no traffic is using a Virtual Channel at the
time it is disabled.
4. Software must fully disable a Virtual Channel in both Components on a
Link before re-enabling the Virtual Channel.
30:27 RO 0h Reserved
26:24 RW 001b
VC1 ID (VC1ID)
Assigns a VC ID to the VC resource. Assigned value must be non-zero. This
field can not be modified when the VC is already enabled.
23:20 RO 0h Reserved
19:17 RW 000b
Port Arbitration Select (PAS)
This field configures the VC resource to provide a particular Port Arbitration
service. The Reset Value of 0h corresponds to bit position of the only
asserted bit in the Port Arbitration Capability field.
16 RO 0b Reserved
15:8 RO 00h Reserved
7:1 RW 00h
TC/VC1 Map (TCVC1M)
This field 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 must ensure that no new or
outstanding transactions with the TC labels are targeted at the given Link.
0RO 0b
TC0/VC1 Map (TC0/VC1M)
Traffic Class 0 is always routed to VC0.