Transmit Flow Control Interface
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 38: 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.
Configuration Control Interface
The Configuration Control interface signals allow a broad range of information exchange
between the user application and the core. The user application uses this interface to do the
following:
Chapter 3: Product Specification
PG346 (v3.3) November 16, 2022
CPM Mode for PCI Express
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