2.4.5 Debug features

The CCI-550 has monitors on all slave and master interfaces that you can use to observe interface status. Each monitor records the number of outstanding read, write, and snoop transactions. It also records the status of the handshake signal from each channel.

This feature can be helpful in the case of a deadlock. For example, the monitors can help to determine outstanding transactions or where back-pressure is being applied.
The monitors are situated inside the outermost registers of the CCI-550. This location means that the numbers of pipeline stages that are configured in a specific implementation affect the values that the monitors indicate.

Note

If the debug registers are accessed through the CCI-550, you might not be able to read the registers in the case of a deadlock.

Trace signaling

CCI-550 supports trace signaling, where each slave interface includes the following 1-bit signals:

  • ARTRACE.
  • RTRACE.
  • AWTRACE.
  • BTRACE.
The CCI-550 receives read and write transaction requests on the slave interfaces and issues corresponding downstream requests from the master interfaces. If the AxTRACES input is HIGH on the incoming request, the corresponding AxTRACEM output is HIGH for the downstream request.
The CCI-550 receives responses on the master interfaces and issues them to the originating device on the slave interfaces. If the RTRACEM input is HIGH, the corresponding RTRACES output is HIGH when the response is sent upstream.
In the case of a snoop hit, the CCI does not issue the request downstream and RTRACES is LOW.
In the case of an Evict transaction, the CCI generates a response and BTRACES is LOW.

Note

The CCI does not include trace signals on the snoop interfaces.
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