PMCCNTR_EL0 | Jon's Arm Reference

Holds the value of the processor Cycle Counter, CCNT, that counts processor clock cycles. For more information, see 'Time as measured by the Performance Monitors cycle counter'.

PMU.PMCCFILTR_EL0 determines the modes and states in which the PMCCNTR_EL0 can increment.

Configuration

External register PMCCNTR_EL0 bits [63:0] are architecturally mapped to AArch64 System register PMCCNTR_EL0[63:0].

External register PMCCNTR_EL0 bits [63:0] are architecturally mapped to AArch32 System register PMCCNTR[63:0].

This register is present only when FEAT_PMUv3_EXT is implemented. Otherwise, direct accesses to PMCCNTR_EL0 are RES0.

Attributes

Field descriptions

CCNT, bits [63:0]

Cycle count. Depending on the values of PMU.PMCR_EL0.{LC,D}, the cycle count increments in one of the following ways:

Every processor clock cycle.
Every 64th processor clock cycle.

Writing 1 to PMU.PMCR_EL0.C sets this field to 0.

The reset behavior of this field is:

On a Warm reset, this field resets to an architecturally UNKNOWN value.

Accessing PMCCNTR_EL0

Note

SoftwareLockStatus() depends on the type of access attempted and AllowExternalPMUAccess() has a new definition from Armv8.4. Refer to the Pseudocode definitions for more information.

Accesses to this register use the following encodings:

When FEAT_PMUv3_EXT64 is implemented

[63:0] Accessible at offset 0x0F8 from PMU

When DoubleLockStatus(), or !IsCorePowered(), or OSLockStatus() or !AllowExternalPMUAccess(), accesses to this register generate an error response.
Otherwise, accesses to this register are RW.

When FEAT_PMUv3_EXT32 is implemented

[31:0] Accessible at offset 0x0F8 from PMU

When DoubleLockStatus(), or !IsCorePowered(), or OSLockStatus() or !AllowExternalPMUAccess(), accesses to this register generate an error response.
When SoftwareLockStatus(), accesses to this register are RO.
Otherwise, accesses to this register are RW.

When FEAT_PMUv3_EXT32 is implemented

[63:32] Accessible at offset 0x0FC from PMU

When DoubleLockStatus(), or !IsCorePowered(), or OSLockStatus() or !AllowExternalPMUAccess(), accesses to this register generate an error response.
When SoftwareLockStatus(), accesses to this register are RO.
Otherwise, accesses to this register are RW.

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
CCNT
CCNT

PMCCNTR_EL0: Performance Monitors Cycle Counter

Purpose

Configuration

Attributes

Field descriptions

CCNT, bits [63:0]

Accessing PMCCNTR_EL0