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RMR_EL1, Reset Management Register (EL1)

The RMR_EL1 characteristics are:

Purpose

If EL1 is the highest implemented Exception level and this register is implemented:

  • A write to the register at EL1 can request a Warm reset.
  • If EL1 can use AArch32 and AArch64, this register specifies the Execution state that the PE boots into on a Warm reset.

Configuration

AArch64 System register RMR_EL1 bits [31:0] are architecturally mapped to AArch32 System register RMR[31:0] when IsHighestEL(EL1).

Only implemented if EL1 is the highest implemented Exception level. In this case:

  • If EL1 can use AArch32 and AArch64 then this register must be implemented.
  • If EL1 cannot use AArch32 then it is IMPLEMENTATION DEFINED whether the register is implemented.

Some or all RW fields of this register have defined reset values. These apply only if the PE resets into an Exception level that is using AArch64. Otherwise, RW fields in this register reset to architecturally UNKNOWN values.

Attributes

RMR_EL1 is a 64-bit register.

Field descriptions

The RMR_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0
RES0RRAA64
313029282726252423222120191817161514131211109876543210

Bits [63:2]

Reserved, RES0.

RR, bit [1]

Reset Request. Setting this bit to 1 requests a Warm reset.

This field resets to 0.

AA64, bit [0]

When EL1 can use AArch32, determines which Execution state the PE boots into after a Warm reset:

AA64Meaning
0b0

AArch32.

0b1

AArch64.

On coming out of the Warm reset, execution starts at the IMPLEMENTATION DEFINED reset vector address of the specified Execution state.

If EL1 cannot use AArch32 this bit is RAO/WI.

When implemented as a RW field, this field resets to 1 on a Cold reset.

Accessing the RMR_EL1

Accesses to this register use the following encodings:

MRS <Xt>, RMR_EL1

op0op1CRnCRmop2
0b110b0000b11000b00000b010
if PSTATE.EL == EL1 && IsHighestEL(EL1) then
    return RMR_EL1;
else
    UNDEFINED;
              

MSR RMR_EL1, <Xt>

op0op1CRnCRmop2
0b110b0000b11000b00000b010
if PSTATE.EL == EL1 && IsHighestEL(EL1) then
    RMR_EL1 = X[t];
else
    UNDEFINED;
              


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