GTS AXI Streaming Intel® FPGA IP for PCI Express* Design Example User Guide

ID 817713
Date 11/04/2024
Public
Document Table of Contents

1.2.2.6. TX Credit Initialization

In the GTS AXI Streaming IP, the back pressure mechanism by the PIO is done through the credit system. Therefore, the credit value must be declared during the credit initialization stage.

An initial TX credit value is captured by the CRDT_INIT and is deducted for any TLP sent to the DUT. When the credit reaches zero, the DUT ceases sending further TLP until the credit is returned by the DUT. This block interfaces with the credit signals from the DUT and focus on initializing and return of the TX credit.

For the TX direction, only crdt_init_ack is asserted in the block to complete the initialization stage. The PIO captures the TX credit during the initialization stage which is initiated by the DUT.