MPC8540 datasheet(1092/1302 Pages) FREESCALE

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

19-14

Freescale Semiconductor

Performance Monitor

that, although a burst is identified when the minimum number of events occurs, it is not counted

until the burst sequence has ended. A burst sequence ends when the specified burstiness

granularity is exceeded, at which point the last valid event has occurred for that sequence.

PMLCAn[BGRAN] specifies the maximum number of cycles between individual events for them

to qualify as members of the same burst sequence.

The burstiness distance field (PMLCAn[BDIST]) and threshold/burstiness multiplier field

(PMLCBn[TBMULT]) specify the acceptable number of cycles between the end of a burst

sequence and the beginning of a new sequence for a group of event occurrences to be counted as

an individual burst. The product of the burstiness distance field and the threshold/burstiness

multiplier field determine the burstiness distance value used to determine when another burst

sequence can begin. Note that the burst distance count begins when a new burst sequence ends and

the PMC is incremented. No new burst sequence may begin until the burst distance count has

reached zero. After the burst distance count reaches zero, it holds the zero value indicating that a

new burst sequence can be counted. The burst distance count begins again when a new burst

sequence is identified and counted.

Burstiness counting is disabled when the definition of a burst is ambiguous, that is, when the burst

size field is less than two, or the burst distance is zero. When burstiness counting is disabled,

regular counting is allowed.

Figure 19-10 shows that the burst distance is measured from the end of one burst sequence and that

a new burst sequence may not begin until the burst distance count expires.

Three internal counters track the different values required for burstiness counting.

•

Burstiness size is monitored by a counter. It is loaded with the value specified in the local

control register when the burst granularity counter and the burst distance counters reach

zero, and no new event is occurring. It always decrements when the following conditions

occur: its value is not already zero, an event occurs, and the burst distance count equals

zero.

•

Burstiness granularity is monitored by a counter that is loaded with the specified value in

the local control register on the rising edge of an event occurrence whenever the burst

distance count equals zero. The granularity counter is decremented (if it has not already

reached zero) when an event is not occurring and burst distance count equals zero.

•

Burstiness distance is measured by a counter that is loaded with the product of

PMLCBn[BDIST] and PMLCBn[TBMULT] when a burst sequence has been identified

and counted. This counter is decremented when burstiness counting is enabled (and the

counter has not already reached zero).

A burst is counted at the end of a burst sequence when the three burst parameter counters are all

equal to zero. Figure 19-11 shows a burstiness counting example.

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