Performance Monitor Unit
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
12-17
ID021414
Non-Confidential
To access the PMCR:
MRC p15, 4, <Rt>, c12, c0, 0 ; Read PMCR into Rt
MCR p15, 4, <Rt>, c12, c0, 0 ; Write Rt to PMCR
[6]
LC
Long cycle count enable. Determines which PMCCNTR_EL0 bit generates an overflow recorded in
PMOVSR[31]. The possible values are:
0
Overflow on increment that changes PMCCNTR_EL0[31] from 1 to 0.
1
Overflow on increment that changes PMCCNTR_EL0[63] from 1 to 0.
[5]
DP
Disable cycle counter, PMCCNTR_EL0 when event counting is prohibited:
0
Cycle counter operates regardless of the non-invasive debug authentication settings. This is the
reset value.
1
Cycle counter is disabled if non-invasive debug is not permitted and enabled.
This bit is read/write.
[4]
X
Export enable. This bit permits events to be exported to another debug device, such as a trace macrocell, over
an event bus:
0
Export of events is disabled. This is the reset value.
1
Export of events is enabled.
This bit is read/write and does not affect the generation of Performance Monitors interrupts on the
nPMUIRQ
pin.
[3]
D
Clock divider:
0
When enabled, PMCCNTR_EL0 counts every clock cycle. This is the reset value.
1
When enabled, PMCCNTR_EL0 counts every 64 clock cycles.
This bit is read/write.
[2]
C
Clock counter reset. This bit is WO. The effects of writing to this bit are:
0
No action. This is the reset value.
1
Reset PMCCNTR_EL0 to 0.
This bit is always RAZ.
Note
Resetting PMCCNTR does not clear the PMCCNTR_EL0 overflow bit to 0. See the
ARM
®
Architecture
Reference Manual ARMv8, for ARMv8-A architecture profile
for more information.
[1]
P
Event counter reset. This bit is WO. The effects of writing to this bit are:
0
No action. This is the reset value.
1
Reset all event counters, not including PMCCNTR_EL0, to zero.
This bit is always RAZ.
In Non-secure EL0 and EL1, a write of 1 to this bit does not reset event counters that MDCR_EL2.HPMN
reserves for EL2 use.
In EL2 and EL3, a write of 1 to this bit resets all the event counters.
Resetting the event counters does not clear any overflow bits to 0.
[0]
E
Enable. The possible values of this bit are:
0
All counters, including PMCCNTR_EL0, are disabled. This is the reset value.
1
All counters are enabled.
This bit is RW.
In Non-secure EL0 and EL1, this bit does not affect the operation of event counters that MDCR_EL2.HPMN
reserves for EL2 use.
On Warm reset, the field resets to 0.
Table 12-10 PMCR bit assignments (continued)
Bits
Name
Function