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CNTACR<n>

CNTACR<n>, Counter-timer Access Control Registers, n = 0 - 7

The CNTACR<n> characteristics are:

Purpose

Provides top-level access controls for the elements of a timer frame. CNTACR<n> provides the controls for frame CNTBaseN.

In addition to the CNTACR<n> control:

CNTNSAR controls whether CNTACR<n> is accessible by Non-secure accesses.
If frame CNTEL0BaseN is implemented, the CNTEL0ACR in frame CNTBaseN provides additional control of accesses to frame CNTEL0BaseN.

Configuration

It is IMPLEMENTATION DEFINED whether CNTACR<n> is implemented in the Core power domain or in the Debug power domain.

For more information, see 'Power and reset domains for the system level implementation of the Generic Timer'.

Implemented only if the value of CNTTIDR.Frame<n> is 1.

An implementation of the counters might not provide configurable access to some or all of the features. In this case, the associated field in the CNTACR<n> register is:

RAZ/WI if access is always denied.
RAO/WI if access is always permitted.

Attributes

CNTACR<n> is a 32-bit register.

Field descriptions

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
RES0																										RWPT	RWVT	RVOFF	RFRQ	RVCT	RPCT

Bits [31:6]

Reserved, RES0.

RWPT, bit [5]

Read/write access to the EL1 Physical Timer registers CNTP_CVAL, CNTP_TVAL, and CNTP_CTL, in frame <n>.

RWPT	Meaning
0b0	No access to the EL1 Physical Timer registers in frame <n>. The registers are RES0.
0b1	Read/write access to the EL1 Physical Timer registers in frame <n>.

The reset behavior of this field is:

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

RWVT, bit [4]

Read/write access to the Virtual Timer register CNTV_CVAL, CNTV_TVAL, and CNTV_CTL, in frame <n>.

RWVT	Meaning
0b0	No access to the Virtual Timer registers in frame <n>. The registers are RES0.
0b1	Read/write access to the Virtual Timer registers in frame <n>.

The reset behavior of this field is:

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

RVOFF, bit [3]

Read-only access to CNTVOFF, in frame <n>.

RVOFF	Meaning
0b0	No access to CNTVOFF in frame <n>. The register is RES0.
0b1	Read-only access to CNTVOFF in frame <n>.

The reset behavior of this field is:

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

RFRQ, bit [2]

Read-only access to CNTFRQ, in frame <n>.

RFRQ	Meaning
0b0	No access to CNTFRQ in frame <n>. The register is RES0.
0b1	Read-only access to CNTFRQ in frame <n>.

The reset behavior of this field is:

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

RVCT, bit [1]

Read-only access to CNTVCT, in frame <n>.

RVCT	Meaning
0b0	No access to CNTVCT in frame <n>. The register is RES0.
0b1	Read-only access to CNTVCT in frame <n>.

The reset behavior of this field is:

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

RPCT, bit [0]

Read-only access to CNTPCT, in frame <n>.

RPCT	Meaning
0b0	No access to CNTPCT in frame <n>. The register is RES0.
0b1	Read-only access to CNTPCT in frame <n>.

The reset behavior of this field is:

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

Accessing CNTACR<n>

In a system that supports the Realm Management Extension, CNTNSAR.NS<n> describes how these registers can be accessed by Root or Realm accesses.

In a system that recognizes two Security states:

CNTACR<n> is always accessible by Secure accesses.
CNTNSAR.NS<n> determines whether CNTACR<n> is accessible by Non-secure accesses.

CNTACR<n> can be accessed through the memory-mapped interfaces:

Component	Frame	Offset	Instance
Timer	CNTCTLBase	0x040 + (4 * n)	CNTACR<n>

Accesses to this register are RW.

2026-03-12 12:23:09, 2025-09_rel_asl1

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