2.5.5. Internal cycle types for cached cores

Table 2.5 shows the meaning of internal cycle types for cached cores.

Table 2.5. Internal cycle types for cached cores

Cycle typesMeaning
F_CyclesFast clock (FLCK) cycles. These are internal core cycles accessing the cache. F_Cycles is not incremented for uncached accesses because the core clock switches to the bus clock.
Core CyclesCore cycles are clock ticks to the core. Core Cycles are incremented for each tick, whether the core is running FCLK (cache accesses) or bus clock (BCLK, non-cache accesses).
True Idle CyclesIdle cycles that are not part of a merged I-S cycle.


If you want to count execution time, use external bus cycle counts (see Cached cores with MMUs or PUs and AMBA ASB interfaces or Cached cores with MMUs or PUs and AMBA AHB interfaces). You cannot use F_Cycles to count execution time, because F_Cycles does not increment for uncached accesses.

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