ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

Debug Registers Reference
C10.9.9 c9, Event Count Register (PMXEVCNTR)
The Event Count Register, PMXEVCNTR, is used to read or write the value of the current event counter,
PMNx. PMSELR selects the current event counter, see c9, Event Counter Selection Register (PMSELR) on
page C10-113.
The PMXEVCNTR is:
a 32-bit read/write CP15 register
accessible in:
— privileged modes
— User mode only when the PMUSERENR.EN bit is set to 1
when the Security Extensions are implemented, a Common register
accessed using an MRC or MCR command with set to c9, set to 0, set to c13, and
set to 2.
The format of the PMXEVCNTR is:
31 0
PMNX
PMNX, bits [31:0]
Value of the current event counter, PMNx.
A read of the PMXEVCNTR always returns the current value of the register.
The contents of each of the Event Count Registers are UNKNOWN on a core logic reset.
Note
You can write to the PMXEVCNTR even when the counter is disabled. This is true regardless of why the
counter is disabled, which can be any of:
because 1 has been written to the appropriate bit in the PMCNTENCLR
because the PMCR.E bit is set to 0
by the non-invasive debug authentication.
C10-116 Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. ARM DDI 0406B