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# TTBCR2, Translation Table Base Control Register 2

The TTBCR2 characteristics are:

## Purpose

The second control register for stage 1 of the PL1&0 translation regime.

If ARMv8.2-AA32HPD is not implemented then this register is not implemented and its encoding is unallocated. Otherwise:

- When the value of TTBCR.{EAE, T2E} is not {1, 1} the contents of TTBCR2 are treated as zero for all purposes other than reading or writing the register.
- When the value of TTBCR.{EAE, T2E} is {1, 1} TTBCR2 is used with TTBCR.

## Configuration

AArch32 System register TTBCR2 bits [31:0] are architecturally mapped to AArch64 System register TCR_EL1[63:32] .

This register is present only from Armv8.2. Otherwise, direct accesses to TTBCR2 are UNDEFINED.

RW fields in this register reset to architecturally UNKNOWN values.

## Attributes

TTBCR2 is a 32-bit register.

## Field descriptions

The TTBCR2 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 | HWU162 | HWU161 | HWU160 | HWU159 | HWU062 | HWU061 | HWU060 | HWU059 | HPD1 | HPD0 | RES0

#### Bits [31:19]

Reserved, RES0.

#### HWU162, bit [18]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[62] of the stage 1 translation table Block or Page entry for translations using TTBR1.

HWU162 | Meaning
--- | ---
0b0 | For translations using TTBR1, bit[62] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR1, bit[62] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD1 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD1 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HWU161, bit [17]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[61] of the stage 1 translation table Block or Page entry for translations using TTBR1.

HWU161 | Meaning
--- | ---
0b0 | For translations using TTBR1, bit[61] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR1, bit[61] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD1 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD1 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HWU160, bit [16]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[60] of the stage 1 translation table Block or Page entry for translations using TTBR1.

HWU160 | Meaning
--- | ---
0b0 | For translations using TTBR1, bit[60] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR1, bit[60] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD1 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD1 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HWU159, bit [15]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[59] of the stage 1 translation table Block or Page entry for translations using TTBR1.

HWU159 | Meaning
--- | ---
0b0 | For translations using TTBR1, bit[59] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR1, bit[59] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD1 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD1 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HWU062, bit [14]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[62] of the stage 1 translation table Block or Page entry for translations using TTBR0.

HWU062 | Meaning
--- | ---
0b0 | For translations using TTBR0, bit[62] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR0, bit[62] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD0 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD0 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HWU061, bit [13]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[61] of the stage 1 translation table Block or Page entry for translations using TTBR0.

HWU061 | Meaning
--- | ---
0b0 | For translations using TTBR0, bit[61] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR0, bit[61] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD0 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD0 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HWU060, bit [12]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[60] of the stage 1 translation table Block or Page entry for translations using TTBR0.

HWU060 | Meaning
--- | ---
0b0 | For translations using TTBR0, bit[60] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR0, bit[60] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD0 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD0 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HWU059, bit [11]
When ARMv8.2-TTPBHA is implemented:

Hardware Use. Indicates IMPLEMENTATION DEFINED hardware use of bit[59] of the stage 1 translation table Block or Page entry for translations using TTBR0.

HWU059 | Meaning
--- | ---
0b0 | For translations using TTBR0, bit[59] of each stage 1 translation table Block or Page entry cannot be used by hardware for an IMPLEMENTATION DEFINED purpose.
0b1 | For translations using TTBR0, bit[59] of each stage 1 translation table Block or Page entry can be used by hardware for an IMPLEMENTATION DEFINED purpose if the value of TTBCR2.HPD0 is 1.

The Effective value of this field is 0 if the value of TTBCR2.HPD0 is 0 or the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HPD1, bit [10]
When ARMv8.2-AA32HPD is implemented:

Hierarchical Permission Disables. This affects the hierarchical control bits, APTable, XNTable, and PXNTable, in the translation tables pointed to by TTBR1.

HPD1 | Meaning
--- | ---
0b0 | Hierarchical permissions are enabled.
0b1 | Hierarchical permissions are disabled if TTBCR.T2E == 1.

When disabled, the permissions are treated as if the bits are 0.

The Effective value of this field is 0 if the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### HPD0, bit [9]
When ARMv8.2-AA32HPD is implemented:

Hierarchical Permission Disables. This affects the hierarchical control bits, APTable, XNTable, and PXNTable, in the translation tables pointed to by TTBR0.

HPD0 | Meaning
--- | ---
0b0 | Hierarchical permissions are enabled.
0b1 | Hierarchical permissions are disabled if TTBCR.T2E ==1.

When disabled, the permissions are treated is as if the bits are 0.

The Effective value of this field is 0 if the value of TTBCR.T2E is 0.

This field resets to an architecturally UNKNOWN value.

####
Otherwise:

Reserved, RES0.

#### Bits [8:0]

Reserved, RES0.

## Accessing the TTBCR2

Accesses to this register use the following encodings:

#### MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b000 | 0b0010 | 0b0000 | 0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T2 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T2 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TRVM == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TRVM == '1' then AArch32.TakeHypTrapException(0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) then if SCR.NS == '0' then return TTBCR2_S; else return TTBCR2_NS; else return TTBCR2; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && ELUsingAArch32(EL3) then return TTBCR2_NS; else return TTBCR2; elsif PSTATE.EL == EL3 then if SCR.NS == '0' then return TTBCR2_S; else return TTBCR2_NS;

#### MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b000 | 0b0010 | 0b0000 | 0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T2 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T2 == '1' then AArch32.TakeHypTrapException(0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SCR.NS == '0' && CP15SDISABLE == HIGH then UNDEFINED; elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SCR.NS == '0' && CP15SDISABLE2 == HIGH then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TVM == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TVM == '1' then AArch32.TakeHypTrapException(0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) then if SCR.NS == '0' then TTBCR2_S = R[t]; else TTBCR2_NS = R[t]; else TTBCR2 = R[t]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && ELUsingAArch32(EL3) then TTBCR2_NS = R[t]; else TTBCR2 = R[t]; elsif PSTATE.EL == EL3 then if SCR.NS == '0' && CP15SDISABLE == HIGH then UNDEFINED; elsif SCR.NS == '0' && CP15SDISABLE2 == HIGH then UNDEFINED; else if SCR.NS == '0' then TTBCR2_S = R[t]; else TTBCR2_NS = R[t];

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

27/03/2019 21:59; e5e4db499bf9867a4b93324c4dbac985d3da9376

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