Visible to Intel only — GUID: lbl1465316906467
Ixiasoft
Visible to Intel only — GUID: lbl1465316906467
Ixiasoft
6.1.6. TX Credit Interface
Flow Control credits are defined for the following TLP categories:
- Posted transactions - TLPs that do not require a response
- Non-Posted transactions - TLPs that require a completion
- Completions - TLPs that respond to non-posted transactions
TLP Type | Category |
---|---|
Memory Write | Posted |
Memory Read Memory Read Lock |
Non-posted |
I/O Read I/O Write |
Non-posted |
Configuration Read Configuration Write |
Non-posted |
Message | Posted |
Completions Completions with Data Completion Locked Completion Lock with Data |
Completions |
Fetch and Add AtomicOp | Non-posted |
Credit Type | Number of Dwords |
---|---|
Header credit - completions | 4 dwords |
Header credit - requests | 5 dwords |
Data credits | 4 dwords |
Signal |
Direction |
Description |
---|---|---|
tx_ph_cdts[7:0] | Output |
Header credit net value for the flow control (FC) posted requests. |
tx_pd_cdts[11:0] | Output |
Data credit net value for the FC posted requests. |
tx_nph_cdts[7:0] | Output |
Header credit net value for the FC non-posted requests. |
tx_npd_cdts[11:0] L-Tile | Output |
Data credit net value for the FC non-posted requests. The tx_npd_cdts[11:0] is not available for H-Tile devices. You can monitor the non-posted header credits to determine if there is sufficient space to transmit the next non-posted data TLP. |
tx_cplh_cdts[7:0] | Output |
Header credit net value for the FC Completion. A value of 0xFF indicates infinite Completion header credits. |
tx_cpld_cdts[11:0]L-Tile | Output |
Data credit net value for the FC Completion. A value of 0xFF indicates infinite Completion data credit. The tx_cpld_cdts[11:0] is not available for H-Tile devices. You can monitor the completion header credits to determine if there is sufficient space to transmit the next non-posted data TLP. The completion TLP size is either the request data size or 64 bytes when the completion is split. For Root Ports or non peer-to-peer Endpoints as the link partner, assume that this credit is infinite. |
tx_hdr_cdts_consumed[1:0] | Output |
Asserted for 1 coreclkout_hip cycle, for each header credit consumed by the application layer traffic. Note that credits the Hard IP consumes for internally generated Completions or Messages are not tracked in this signal. For the Gen3 x16 512-bit interface, tx_hdr_cdts_consumed[1] is for the higher bus and tx_hdr_cdts_consumed[0] is for the lower bus. There is only one tx_hdr_cdts_consumed signal for the 256-bit interface. |
tx_data_cdts_consumed[1:0] | Output |
Asserted for 1 coreclkout_hip cycle, for each data credit consumed. Note that credits the Hard IP consumes for internally generated Completions or Messages are not tracked in this signal. For the Gen3 x16 512-bit interface, tx_data_cdts_consumed[1] is for the higher bus and tx_data_cdts_consumed[0] is for the lower bus. There is only one tx_data_cdts_consumed signal for the 256-bit interface. |
tx_cdts_type[<n>-1:0] | Output | Specifies the credit type shown on the tx_cdts_data_value[1:0] bus. The following encodings are defined:
For the Gen3 x16 512-bit interface, tx_cdts_type[3:2] is for the higher bus and tx_cdts_type[1:0] is for the lower bus. |
tx_cdts_data_value[3:0] L-Tile, 16 lanes tx_cdts_data_value[1:0] L-Tile, 8 lanes or fewer tx_cdts_data_value[1:0] H-Tile, 16 lanes tx_cdts_data_value H-Tile, 8 lanes or fewer |
Output | For H-Tile: 1 = 2 data credits consumed; 0 = 1 data credit consumed. For L-Tile: The value of tx_cdts_data_value+1 specifies the data credit consumed. For both H- and L-Tiles: Only valid when tx_data_cdts_consumed asserts. For the Gen3 x16 512-bit interface, tx_cdts_data_value[1] is for the higher bus and tx_cdts_data_value[0] is for the lower bus. |