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ICC_AP0R<n>
AArch32 Registers
AArch64 Registers
AArch32 Instructions
AArch64 Instructions
Index by Encoding
External Registers
External Registers by Offset
Registers by Functional Group
Proprietary Notice

ICC_AP0R<n>, Interrupt Controller Active Priorities Group 0 Registers, n = 0 - 3

The ICC_AP0R<n> characteristics are:

Purpose

Provides information about Group 0 active priorities.

Configuration

AArch32 System register ICC_AP0R<n> bits [31:0] are architecturally mapped to AArch64 System register ICC_AP0R<n>_EL1[31:0].

This register is present only when FEAT_AA32EL1 is implemented and GICv3 is implemented. Otherwise, direct accesses to ICC_AP0R<n> are UNDEFINED.

Attributes

ICC_AP0R<n> is a 32-bit register.

Field descriptions

313029282726252423222120191817161514131211109876543210
IMPLEMENTATION DEFINED

IMPLEMENTATION DEFINED, bits [31:0]

IMPLEMENTATION DEFINED.

The reset behavior of this field is:

Additional information

The contents of these registers are IMPLEMENTATION DEFINED with the one architectural requirement that the value 0x00000000 is consistent with no interrupts being active.

Accessing ICC_AP0R<n>

Writing to these registers with any value other than the last read value of the register (or 0x00000000 when there are no Group 0 active priorities) might result in UNPREDICTABLE behavior of the interrupt prioritization system, causing:

ICC_AP0R1 is implemented only in implementations that support 6 or more bits of preemption. ICC_AP0R2 and ICC_AP0R3 are implemented only in implementations that support 7 bits of preemption. Unimplemented registers are UNDEFINED.

Note

The number of bits of preemption is indicated by ICH_VTR.PREbits.

Writing to the active priority registers in any order other than the following order will result in UNPREDICTABLE behavior:

Accesses to this register use the following encodings in the System register encoding space:

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>} ; Where m = 0-3

coprocopc1CRnCRmopc2
0b11110b0000b11000b10000b1:m[1:0]

let m:integer = UInt(opc2[1:0]); if !(IsFeatureImplemented(FEAT_AA32EL1) && IsFeatureImplemented(FEAT_GICv3)) then Undefined(); elsif m == 1 && NUM_GIC_PRIORITY_BITS < 6 then Undefined(); elsif (m == 2 || m == 3) && NUM_GIC_PRIORITY_BITS < 7 then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then Undefined(); elsif HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR().FIQ == '1' then Undefined(); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA64EL2) && !ELUsingAArch32(EL2) && HSTR_EL2().T12 == '1' then AArch64_AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA32EL2) && ELUsingAArch32(EL2) && HSTR().T12 == '1' then AArch32_TakeHypTrapException(0x03); elsif ICC_SRE().SRE == '0' then Undefined(); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA64EL2) && !ELUsingAArch32(EL2) && ICH_HCR_EL2().TALL0 == '1' then AArch64_AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA32EL2) && ELUsingAArch32(EL2) && ICH_HCR().TALL0 == '1' then AArch32_TakeHypTrapException(0x03); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA64EL2) && !ELUsingAArch32(EL2) && HCR_EL2().FMO == '1' then R(t) = ICV_AP0R(m); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA32EL2) && ELUsingAArch32(EL2) && HCR().FMO == '1' then R(t) = ICV_AP0R(m); elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_AArch32SystemAccessTrap(EL3, 0x03); end; elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch32_TakeMonitorTrapException(); end; else R(t) = ICC_AP0R(m); end; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then Undefined(); elsif HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && SCR().FIQ == '1' then Undefined(); elsif ICC_HSRE().SRE == '0' then Undefined(); elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_AArch32SystemAccessTrap(EL3, 0x03); end; elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && SCR().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch32_TakeMonitorTrapException(); end; else R(t) = ICC_AP0R(m); end; elsif PSTATE.EL == EL3 then if ICC_MSRE().SRE == '0' then Undefined(); else R(t) = ICC_AP0R(m); end; end;

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>} ; Where m = 0-3

coprocopc1CRnCRmopc2
0b11110b0000b11000b10000b1:m[1:0]

let m:integer = UInt(opc2[1:0]); if !(IsFeatureImplemented(FEAT_AA32EL1) && IsFeatureImplemented(FEAT_GICv3)) then Undefined(); elsif m == 1 && NUM_GIC_PRIORITY_BITS < 6 then Undefined(); elsif (m == 2 || m == 3) && NUM_GIC_PRIORITY_BITS < 7 then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then Undefined(); elsif HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR().FIQ == '1' then Undefined(); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA64EL2) && !ELUsingAArch32(EL2) && HSTR_EL2().T12 == '1' then AArch64_AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA32EL2) && ELUsingAArch32(EL2) && HSTR().T12 == '1' then AArch32_TakeHypTrapException(0x03); elsif ICC_SRE().SRE == '0' then Undefined(); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA64EL2) && !ELUsingAArch32(EL2) && ICH_HCR_EL2().TALL0 == '1' then AArch64_AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA32EL2) && ELUsingAArch32(EL2) && ICH_HCR().TALL0 == '1' then AArch32_TakeHypTrapException(0x03); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA64EL2) && !ELUsingAArch32(EL2) && HCR_EL2().FMO == '1' then ICV_AP0R(m) = R(t); elsif EL2Enabled() && IsFeatureImplemented(FEAT_AA32EL2) && ELUsingAArch32(EL2) && HCR().FMO == '1' then ICV_AP0R(m) = R(t); elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_AArch32SystemAccessTrap(EL3, 0x03); end; elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch32_TakeMonitorTrapException(); end; else ICC_AP0R(m) = R(t); end; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then Undefined(); elsif HaveEL(EL3) && EL3SDDUndefPriority() && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && SCR().FIQ == '1' then Undefined(); elsif ICC_HSRE().SRE == '0' then Undefined(); elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA64EL3) && !ELUsingAArch32(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_AArch32SystemAccessTrap(EL3, 0x03); end; elsif HaveEL(EL3) && IsFeatureImplemented(FEAT_AA32EL3) && ELUsingAArch32(EL3) && SCR().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch32_TakeMonitorTrapException(); end; else ICC_AP0R(m) = R(t); end; elsif PSTATE.EL == EL3 then if ICC_MSRE().SRE == '0' then Undefined(); else ICC_AP0R(m) = R(t); end; end;

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

2026-03-26 20:27:25, 2026-03_rel

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