P-Tile Avalon® Streaming Intel® FPGA IP for PCI Express* User Guide

ID 683059
Date 4/04/2024
Document Table of Contents

4.4.6. Avalon® -ST TX Interface tx_st_ready Behavior

The following timing diagram illustrates the behavior of tx_st_ready_o, which is deasserted to pause the data transmission to the Transaction Layer of the P-Tile IP for PCIe, and then reasserted. The timing diagram shows readyAllowance and readyLatency, both for three cycles. For readyAllowance, the application deasserts tx_st_valid_i three cycles after tx_st_ready_o is deasserted.

The application must not deassert tx_st_valid_i between tx_st_sop_i and tx_st_eop_i on a ready cycle unless there is backpressure with the deassertion of tx_st_ready_o. A ready cycle is a cycle during which the sink can accept a transfer.

Note: This is an additional requirement for the P-Tile IP for PCIe that is not compliant to the Avalon® -ST standard.
Figure 26.  Avalon® -ST TX Interface tx_st_ready Behavior