6.2.3. Capture rates

If a TPIU in continuous mode is used, all port widths from 1 to 32 can be output by the target. Half-rate clocking enables data to be output from the ETM on both edges of TRACECLK. This effectively halves the clock frequency for the same data rate.

The RealView Trace 2 unit can trace data at a maximum rate of 400MHz using normal clocking mode, or 200MHz using half-rate clocking mode.

The type of application can affect the instructions that can be captured. For example, trace figures for automotive applications are different to those for telecomms applications. Table 6.1 and Table 6.2 provide a comparison between RVT and RVT2 for an ETM v3 core under a number of different trace configurations.

Table 6.1. Trace buffer utilization comparisons - automotive

  RVT1  RVT2  
Port WidthTimestampsPackingSamples capturedInstructions tracedPackingSamples capturedInstructions traced
4No88,388,60826,886,5642450,331,648161,319,385
4Yes44,194,30413,443,2821633,554,432107,546,256
8No44,194,30426,886,5641225,165,824161,319,385
8Yes22,097,15213,443,282816,777,216107,546,256

A sample is the data captured on one clock edge (for SDR or DDR). The data shown in Table 6.1 is based on instruction-only, cycle-approximate trace capture. The bytes of instruction trace per instruction is assumed to be 0.156 (automotive).

Table 6.2. Trace buffer utilization comparisons - telecomms

  RVT1  RVT2  
Port WidthTimestampsPackingSamples capturedInstructions tracedPackingSamples capturedInstructions traced
4No88,388,60856,679,7842450,331,648340,078,703
4Yes44,194,30428,339,8921633,554,432226,719,135
8No44,194,30456,679,7841225,165,824340,078,703
8Yes22,097,15228,339,892816,777,216226,719,135

A sample is the data captured on one clock edge (for SDR or DDR). The data shown in Table 6.2 is based on instruction-only, cycle-approximate trace capture. The bytes of instruction trace per instruction is assumed to be 0.074 (telecomms).

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