AXI Transactions in the Waveform Viewer - 2022.2 English

Vivado Design Suite User Guide: Programming and Debugging (UG908)

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2022.2 English

Transactions associated with AXI3, AXI4, and AXI4-Lite interfaces that are being debugged by the System ILA can be viewed in the waveform viewer as shown in the following figure

Figure 1. AXI Transactions in the Waveform Viewer

AXI transactions are defined as follows:

  • Read transactions start with the beginning of the Address Command event on the AR (Read Address) channel.
  • Read transactions end with the Last Read Data event on the R (Read Data) channel.
  • Write transactions start with the beginning of the Address Command event on the AW (Write Address) channel.
  • Write transactions end with the Write Response event on the B (Write Response) channel.

Transactions are only shown when the address, data, and/or response events have matching IDs. In addition, transactions are only shown in the waveform if both the start and end events occur within the captured data waveform. When multiple outstanding/overlapping transactions are displayed in the Waveform window, multiple transaction rows are used.

It is possible that the transactions on the interface can cause the outstanding transaction tracking logic within the System ILA IP to overflow as shown in the following figure.

Figure 2. AXI Transaction Counter Overflow Condition

Two overflow conditions can result:

  • The number of outstanding transactions for a particular ID overflow the transaction counter capacity.
  • The number of IDs that have outstanding transactions overflow the number of available counters.

In either case, an overflow condition can be resolved by re-customizing the System ILA core in the IP integrator block design to increase the number of outstanding read and/or write transactions. See the following figure.

Figure 3. Increasing the Number of Outstanding Transactions That Can Be Tracked by System ILA