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

ID 790711
Date 2/12/2024
Public

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6.5.2. Configuration Intercept Response Interface (st_ciiresp)

The application must return the response for request received on "st_ciireq" interface using "st_ciiresp" interface. The IP is always ready to accept responses from the application. The application will provide response data with valid qualifier.

This interface is applicable only when operating as Endpoint in Power User mode. It is mutually exclusive with the Configuration Extension Bus Response Interface.

Table 47.  Configuration Intercept Response Interface
Signal Name Direction Clock Domain Description
app_ss_st_ciiresp_tvalid Input axi_lite_clk Application asserts this signal for one clock to indicate that valid data is driven on app_ss_st_ciiresp_tdata bus.
app_ss_st_ciiresp_tdata[31:0] Input axi_lite_clk

Override data from application for the intercepted configuration request on "st_ciireq interface".

For CfgWr: override the write data to the Configuration register with data supplied by the application logic.

For CfgRd: override the data payload of the completion TLP with data supplied by the application logic.

app_ss_st_ciiresp_tdata[32] Input axi_lite_clk

Override Data Enable:

Application assert this signal to override the CfgWr payload or CfgRd completion using the data supplied by the application logic on app_ss_st_ciiresp_tdata[31:0] bus.

The following figure shows timing diagram for back-to-back read and write request; the first request sends configuration read on st_ciireq interface for all four bytes of register located at address=0x8. Application decides not to intercept this configuration read and hence return tvalid=1 together with tdata[32]=0 on the st_ciiresp interface.

After receiving the first response on the st_ciiresp interface, the second request sends configuration write for byte0, byte1 and byte2 of register located at address=0x4 with data value of 0xABC. Application decides to intercept this configuration write and hence return tvalid=1 together with tdata[32]=1 on the st_ciiresp interface. Additionally, application provides the data (i.e., 0xDEF) to be used for the intercepted configuration write on the st_ciiresp interface through tdata[31:0].

Figure 41. Timing Diagram for Configuration Intercept Interface