11-6
MPC7400 RISC Microprocessor Users Manual
Special-Purpose Registers Used by the Performance Monitor
7D8
TBSEL
Time base selector. Selects the time base bit that can cause a time base transition event
(the event occurs when the selected bit changes from 0 to 1).
00 TB[63] (TBL[31])
01 TB[55] (TBL[23])
10 TB[51] (TBL[19])
11 TB[47] (TBL[15])
Time base transition events can be used to periodically collect information about processor
activity. In multiprocessor systems in which TB registers are synchronized among
processors, time base transition events can be used to correlate the performance monitor
data obtained by the several processors. For this use, software must specify the same
TBSEL value for all the processors in the system. Because the time-base frequency is
implementation-dependent, software should invoke a system service program to obtain the
frequency before choosing a value for TBSEL.
9
TBEE
Time base event enable.
0 Time-base transition events are disabled.
1 Time-base transition events are enabled. A timebase transition is signaled to the
performance monitor if the TB bit speciTed in MMCR0[TBSEL] changes from 0 to 1.
Time-base transition events can be used to freeze the counters (MMCR0[FCECE]),
trigger the counters (MMCR0[TRIGGER]), or signal an exception (MMCR0[PMXE]).
Changing the bits speciTed in MMCR0[TBSEL] while MMCR0[TBEE] is enabled may cause
a false 0 to 1 transition that signals the speciTed action (freeze, trigger, or exception) to
occur immediately.
10D15 THRESHOLD
Threshold. Contains a threshold value, which is a value such that only events that exceed
the value are counted (PMC1 events 11, 19, and 20).
By varying the threshold value, software can obtain a proTle of the characteristics of the
events subject to the threshold. For example, if PMC1 counts cache misses for which the
duration exceeds the threshold value, software can obtain the distribution of cache miss
durations for a given program by monitoring the program repeatedly using a different
threshold value each time.
Note that MMCR2[THRESHMULT] chooses whether this value is multiplied by 2 or 32.
16
PMC1CE
PMC1 condition enable. Controls whether counter negative conditions due to a negative
value in PMC1 are enabled.
0 Counter negative conditions for PMC1 are disabled.
1 Counter negative conditions for PMC1 are enabled. These events can be used to freeze
the counters (MMCR0[FCECE]), trigger the counters (MMCR0[TRIGGER]), or signal an
exception (MMCR0[PMXE]).
17
PMCjCE
PMCj condition enable. Controls whether counter negative conditions due to a negative
value in any PMCj (that is, in any PMC except PMC1) are enabled.
0 Counter negative conditions for all PMCjs are disabled.
1 Counter negative conditions for all PMCjs are enabled. These events can be used to
freeze the counters (MMCR0[FCECE]), trigger the counters (MMCR0[TRIGGER]), or
signal an exception (MMCR0[PMXE]).
Table 11-3. MMCR0 Field Descriptions (Continued)
Bits
Name
Description