Scalable Scatter-Gather DMA Intel® FPGA IP User Guide

ID 823097
Date 1/27/2025
Public
Document Table of Contents

4.2.4. Transmit Flow Control Credit Interface

This interface provides the link partner's receive buffer space information. The interface provides posted, non-posted, completion data, and header credit information. One data credit equals to four dwords (DWs) and one header credit is equal to the max size header plus optional digest field. Connect this interface to Transmit Flow Control Credit interface of GTS AXI Streaming Intel® FPGA IP for PCI Express.

Clock Domain: ss_axi_st_clk

Table 39.  Transmit Flow Control Credit Interface
Signal Name Direction Description
ss_app_st_txcrdt_tvalid IN When asserted indicates that the credit information on tdata is valid
ss_app_st_txcrdt_tdata[18:0] IN

Carries credit limit information and type of credit

Bit[15:0] - Credit Limit Value

Bit[18:16] - Credit Type

3'b000 - Posted Header Credit

3'b001 - Non-Posted Header Credit

3'b010 - Completion Header Credit

3'b011 - Reserved

3'b100 - Posted Data Credit

3'b101 - Non-Posted Data Credit

3'b110 - Completion Data Credit

3'b111 - Reserved