Transmit Flow Control Interface - 3.4 English

Versal Adaptive SoC CPM Mode for PCI Express Product Guide (PG346)

Document ID
PG346
Release Date
2024-05-30
Version
3.4 English

The following table defines the transmit flow control interface ports of the core.

Note: The pcie0* signals map to PCIe Controller 0 and pcie1* signals map to PCIe Controller 1 in the port descriptions below.
Table 1. Transmit Flow Control Interface Port Description
Port I/O Width Description

pcie0_pcie_tfc_nph_av

pcie1_pcie_tfc_nph_av

O 4 This output provides an indication of the currently available header credit for Non-Posted TLPs on the transmit side of the core. The user logic can check this output before transmitting a Non-Posted request on the requester request interface to avoid blocking the interface when no credit is available. The encodings are:
  • 0000: No credit available
  • 0001: 1 credit available
  • 0010: 2 credits available
  • ...
  • 1110: 14 credits available
  • 1111: 15 or more credits available

Because of pipeline delays, the value on this output can not include the credit consumed by the Non-Posted requests in the last eight cycles or less. The user logic must adjust the value on this output by the credit consumed by the Non-Posted requests it sent in the previous clock cycles, if any.

pcie0_pcie_tfc_npd_av

pcie1_pcie_tfc_npd_av

O 4 This output provides an indication of the currently available payload credit for Non-Posted TLPs on the transmit side of the core. The user logic checks this output before transmitting a Non-Posted request on the requester request interface to avoid blocking the interface when no credit is available. The encodings are:
  • 0000: No credit available
  • 0001: 1 credit available
  • 0010: 2 credits available
  • ...
  • 1110: 14 or more credits available
  • 1111: 15 or more credits available

Because of pipeline delays, the value on this output does not include the credit consumed by the Non-Posted requests sent by the user logic in the last eight clock cycles or less. The user logic must adjust the value on this output by the credit consumed by the Non-Posted requests it sent in the previous clock cycles, if any.