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

ID 683059
Date 10/07/2021

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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 a readyLatency of three cycles. Refer to the Avalon® Interface Specifications for a detailed definition of readyLatency. 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. For the definition of a ready cycle, refer to the Avalon® Interface Specifications.

Note: This is an additional requirement for the P-Tile IP for PCIe that is not compliant to the Avalon® -ST standard.
Figure 32.  Avalon® -ST TX Interface tx_st_ready Behavior