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3.3.9. Mode Register

The MODE Register characteristics are:

Purpose

Controls TMC operating mode.

When configured as an ETB or ETR, the TMC can operate in the following modes:

  • Software FIFO mode

  • Circular Buffer mode.

When configured as an ETF, the TMC has an additional mode of operation, Hardware FIFO mode.

The operating mode can be changed only when the TMC is disabled. Attempting to write to this register while not in Disabled state results in Unpredictable behavior. The operating mode is ignored when in Disabled state.

Configurations

Present in all configurations.

Figure 3.9 shows the MODE Register bit assignments.

Figure 3.9. MODE Register bit assignments

Figure 3.9. MODE Register bit assignments

Table 3.10 shows the MODE Register bit assignments.

Table 3.10. MODE Register bit assignments
BitsNameFunction
[31:2]Reserved

Reserved.

[1:0]MODE

Selects the operating mode. The following are the operation modes:

3 =Reserved

Reserved

2 = Hardware FIFO mode

This mode is available only in the ETF configuration.

Enabling this mode in any other configuration results in Unpredictable behavior.

In this mode, the trace memory is used as a FIFO that is drained through the ATB master interface. Trace data is captured into the Trace RAM and when full, the incoming trace stream is stalled. When the Trace buffer is non-empty, trace data is drained out through the ATB master interface.

1 = Software FIFO mode

In this mode, the trace memory is used as a FIFO that can be read through the RRD Register while trace is being captured. Trace data is captured into the Trace RAM and when full, the incoming trace stream is stalled.

0 = Circular Buffer mode

In this mode, the trace memory is used as a Circular Buffer. Trace data is captured into the Trace memory starting from the location pointed to by the write pointer register. Even when the trace memory is full, incoming trace data continues to be overwritten into the trace memory until a stop condition has occurred. See Formatter and Flush Control Register and Control Register.

For more information about standard usage models in different modes, see Standard usage models for the TMC.


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