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# CNTNSAR, Counter-timer Non-secure Access Register

The CNTNSAR characteristics are:

## Purpose

Provides the highest-level control of whether frames CNTBaseN and CNTEL0BaseN are accessible by Non-secure accesses.

## Configuration

The power domain of CNTNSAR is IMPLEMENTATION DEFINED.

On a reset of the reset domain in which it is implemented, RW fields in this register reset to UNKNOWN values. The register is not affected by a reset of any other reset domain. For more information see 'Power and reset domains for the system level implementation of the Generic Timer' in Chapter I1 of the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

## Attributes

CNTNSAR is a 32-bit register.

## Field descriptions

The CNTNSAR bit assignments are:

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 | NS7 | NS6 | NS5 | NS4 | NS3 | NS2 | NS1 | NS0

#### Bits [31:8]

Reserved, RES0.

#### NS<n>, bit [n], for n = 0 to 7

Non-secure access to frame n. The possible values of this bit are:

NS<n> | Meaning
--- | ---
0b0 | Secure access only. Behaves as RES0 to Non-secure accesses.
0b1 | Secure and Non-secure accesses permitted.

This bit also determines whether, in the CNTCTLBase frame, CNTACR<n> and CNTVOFF<n> are accessible to Non-secure accesses.

If frame CNTBase<n>:

- Is not implemented, then NS<n> is RES0.
- Is not Configurable access, and is accessible only by Secure accesses, then NS<n> is RES0.
- Is not Configurable access, and is accessible by both Secure and Non-secure accesses, then NS<n> is RES1.

This field resets to an architecturally UNKNOWN value.

## Accessing the CNTNSAR

In a system that recognizes two Security states, this register is only accessible by Secure accesses.

#### CNTNSAR can be accessed through the memory-mapped interfaces:

Component | Frame | Offset | Instance
--- | --- | --- | ---
Timer | CNTCTLBase | 0x004 | CNTNSAR

Access on this interface is RW.

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15/04/2019 16:47; 8c23526ba8a13a72aada4137daf3e3977b49036e

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