MPC8540 datasheet(1091/1302 Pages) FREESCALE

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Functional Description

MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

Freescale Semiconductor

19-13

control register of counter PMC1. This is done by appropriately setting the trigger-on select bit or

trigger-off select bit (PMLCB1[TRIGOFFSEL] or PMLCB1[TRIGONSEL]). Additionally, the

condition that triggers the counter must be selected by configuring the corresponding control bits

(PMLCB1[TRIGONCNTL] or PMLCB1[TRIGOFFCNTL]). Assuming the counter is enabled by

other control register settings, the counter increments (or freezes) when its specified event occurs

after the trigger-on (or off) condition occurs.

When trigger on and trigger off are both selected, the trigger-off condition is ignored until the

trigger-on condition has occurred. Furthermore, when a trigger-off condition occurs, the counter

state is preserved; it is not restarted by subsequent trigger-on conditions.

Triggering is disabled when the counter’s trigger-select bits specify itself as the trigger source.

Similarly, triggering is disabled when the trigger control bits are cleared.

19.4.6 Burstiness Counting

The burstiness counting feature makes it easier to characterize events that occur in rapid

succession followed by a relatively long pause. As shown in Table 19-9, event bursts are defined

by size, granularity, and distance.

Figure 19-10 shows the relationships between size, granularity, and distance. Burstiness counting

can be performed for all events except threshold events.

Figure 19-10. Burst Size, Distance, Granularity, and Burstiness Counting

The burstiness size field (PMLCAn[BSIZE]) specifies the minimum number of event occurrences

that constitute a burst. A burst is identified when the number of event occurrences equals or

exceeds PMLCAn[BSIZE]. Furthermore, these individual event occurrences must be separated by

no more clock cycles than the value in the burstiness granularity field (PMLCAn[BGRAN]). Note

Table 19-9. Burst Definition

Parameter

Description

Size

The minimum number of events constituting a burst

PMLCAn [BSIZE]

Granularity The maximum time between individual events counted as members of the same burst PMLCAn [BGRAN]

Distance

The minimum time between bursts

PMLCAn [BDIST] x

PMLCBn[TBMULT]

Burst size

Burst granularity

Event occurrence

Time

Burst size

Burst distance

(cycles)

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