AXI Multichannel DMA Intel® FPGA IP for PCI Express* User Guide

ID 817911
Date 7/22/2024
Public
Document Table of Contents

4.4.1. PCIe AXI-ST TX Interface (ss_tx_st)

The outbound packet towards the link is transmitted through this PCIe AXI-ST TX interface with separate header and data interfaces. These interfaces support up to 4 segments of 256-bits with a maximum of 2 Transaction Layer Packets (TLPs) per cycle.

For information on this interface, refer to Application Logic Guidelines for the AXI Streaming TX Interface in HIP Native Mode (R-Tile) section in the AXI Streaming Intel FPGA IP for PCI Express User Guide.

Interface clock: axi_st_clk

NUM_OF_SEG depends on the data width.

NUM_OF_SEG = DWIDTH / SEG_WIDTH

DWIDTH = NUM_OF_SEG * 256

DWIDTH depends on the PCIe mode selected. It is equal to:
  • 1024 bits for Gen5 1x16.
  • 512 bits for Gen5 2x8, Gen4 1x16, and Gen3 1x16.
  • 256 bits for Gen4 2x8, and Gen3 2x8.
Table 13.  PCIe AXI-ST TX Interface
Signal Name Direction Description
app_ss_st_tx_tvalid Output

Indicates that the source is driving a valid transfer.

ss_app_st_tx_tready Input

Indicates that the sink can accept a transfer in the current cycle.

Note: The readyLatency parameter defined in Avalon specification is supported. By default, the value is '0'.
app_ss_st_tx_tdata[DWIDTH-1:0] Output

Data interface with configurable width specified by DATA_WIDTH parameter.

Gen5 1x16 DWIDTH: 4 segments x 256 = 1024

app_ss_st_tx_tkeep[DWIDTH/8-1:0] Output

A byte qualifier used to indicate whether the content of the associated byte is valid.

The invalid bytes are allowed only during app_ss_st_tx_tlast cycle.

Note: The sparse tkeep is not allowed.
app_ss_st_tx_tlast Output

Indicates End of Data/Command Transmission

app_ss_st_tx_tuser_last_segment

[NUM_OF_SEG-1:0]

Output

Indicates the last segment of the packet on tdata bus.

For a packet without data payload, this signal is asserted during the header cycle on tuser_hdr bus.

app_ss_st_tx_tuser_hvalid

[NUM_OF_SEG-1:0]

Output

Indicates the tuser_hdr is valid in the respective segment.

app_ss_st_tx_tuser_hdr[DWIDTH-1:0] Output

Carries header format for the respective segment.

For the bit positions and mapping, refer to Header Format section in the AXI Streaming Intel FPGA IP for PCI Express User Guide.