User guide

82 www.xilinx.com Virtex-5 FPGA Integrated Endpoint Block

UG197 (v1.5) July 22, 2009

Chapter 4: Integrated Endpoint Block Operation

Link Retrain Due to an Absence of UpdateFC DLLPs

When the partner device advertises infinite header and data credits for all packet types for

a given virtual channel, the integrated Endpoint block might not receive any UpdateFC

DLLPs. When the integrated Endpoint block does not receive any UpdateFC DLLPs, it

initiates a link retrain because an internal timer used to track the receipt of UpdateFC

DLLPs has expired. This behavior is non-compliant.

Workaround

The partner device should be configured to have at least one packet type per virtual

channel advertising the finite header and data credits.

No workarounds are implemented in LogiCORE Endpoint Block Plus or LogiCORE

Endpoint Block for PCI Express Designs.

Automatic Transmission of PME_TO_Ack Message

The integrated Endpoint block automatically sends a PME_TO_Ack message in response

to a received PME_Turn_Off message instead of allowing the user to control the

transmission of the PME_Turn_Off message.

Workaround

There are no workarounds to prevent the transmission of the PME_Turn_Off. Any

required housekeeping must be completed within 250 ns from the receipt of

PME_Turn_Off message in preparation for power removal. The receipt of PME_Turn_Off

message is indicated by a transition to 1 on the

L0PWRTURNOFFREQ port. This is described

in Table 2-15, page 45.

No workarounds are implemented in LogiCORE Endpoint Block Plus or LogiCORE

Endpoint Block for PCI Express Designs.

48-Packet Threshold on Posted Packets Passing Non-posted and

Completion Packets in the TX Direction

If non-posted packets and completion packets are stalled inside the integrated Endpoint

block’s transmit buffer and more than 48 packets pass a given stalled packet, then the

following scenarios can occur:

• Subsequent posted packets might get stalled until the stalled non-posted or

completion packet is transmitted.

• Older non-posted and completion packets could become younger and will be

incorrectly blocked by a posted packet that arrives later. These non-posted and

completion packets are transmitted if all posted packets that were in the transmit

buffer when the blocking occurred are eventually transmitted.

• A nullified TLP can be transmitted.