B2.30 CPUPOR_EL3, CPU Private Operation Register, EL3

The CPUPOR_EL3 provides IMPLEMENTATION DEFINED configuration and control options for the core.

Bit field descriptions

CPUPOR_EL3 is a 64-bit register, and is part of the IMPLEMENTATION DEFINED registers functional group.

Figure B2-26 CPUPOR_EL3 bit assignments
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Reserved, [63:0]
Reserved for Arm® internal use.
CPUPOR_EL3 is only accessible in Secure state.

Usage constraints

Accessing the CPUPOR_EL3

The CPUPOR_EL3 can be written only when the system is idle. Arm recommends that you write to this register after a powerup reset, before the MMU is enabled.

Writing to this register might cause UNPREDICTABLE behaviors. Therefore, Arm strongly recommends that you do not modify this register unless directed by Arm.

This register is accessible as follows:

This register can be read with the MRS instruction using the following syntax:

MRS <Xt>,<systemreg>

This register can be written with the MSR instruction using the following syntax:

MSR <systemreg>, <Xt>

This syntax is encoded with the following settings in the instruction encoding:

<systemreg> op0 op1 CRn CRm op2
S3_6_C15_8_2 11 110 1111 1000 010

This register is accessible in software as follows:

<systemreg> Control Accessibility
S3_6_C15_8_2 x x 0 - - n/a RW
S3_6_C15_8_2 x 0 1 - - - RW
S3_6_C15_8_2 x 1 1 - n/a - RW

'n/a' Not accessible. The core cannot be executing at this Exception level, so this access is not possible.

Traps and enables

For a description of the prioritization of any generated exceptions, see Synchronous exception prioritization in the Arm® Architecture Reference Manual Armv8, for Armv8-A architecture profile.

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