Vitis Networking P4 could issue back-pressure on the S_AXIS interface by bringing the TREADY signal Low. This can happen in the following scenarios:
- TREADY is Low at the M_AXIS interface.
- Back-pressure is generated within the Deparser because of header insertions extending a packet's length.
- Back-pressure is generated by the CAMs if they are using TDM and if the specified Packet Rate is exceeded and causing excessive table lookup requests (see Top Level Settings for a description of the Packet Rate parameter).
- Back-pressure is generated by the Packet Rate Limiter (when enabled) to prevent the input stream exceeding the specified packet rate.
- Back-pressure is generated for a few clock cycles post
s_axis_aresetn.
When there are CAMs present in the design, it takes a few clock cycles to stop back-pressure after it has been applied. If CAMs are not present, back-pressure stops instantly.