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# ICC_MCTLR, Interrupt Controller Monitor Control Register

The ICC_MCTLR characteristics are:

## Purpose

Controls aspects of the behavior of the GIC CPU interface and provides information about the features implemented.

## Configuration

AArch32 System register ICC_MCTLR bits [31:0] can be mapped to AArch64 System register ICC_CTLR_EL3[31:0] , but this is not architecturally mandated.

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 AArch32. Otherwise, RW fields in this register reset to architecturally UNKNOWN values.

## Attributes

ICC_MCTLR is a 32-bit register.

## Field descriptions

The ICC_MCTLR 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 | ExtRange | RSS | nDS | RES0 | A3V | SEIS | IDbits | PRIbits | RES0 | PMHE | RM | EOImode_EL1NS | EOImode_EL1S | EOImode_EL3 | CBPR_EL1NS | CBPR_EL1S

#### Bits [31:20]

Reserved, RES0.

#### ExtRange, bit [19]

Extended INTID range (read-only).

ExtRange | Meaning
--- | ---
0b0 | CPU interface does not support INTIDs in the range 1024..8191. Behavior is UNPREDICTABLE if the IRI delivers an interrupt in the range 1024 to 8191 to the CPU interface. Note Arm strongly recommends that the IRI is not configured to deliver interrupts in this range to a PE that does not support them.
0b1 | CPU interface supports INTIDs in the range 1024..8191 All INTIDs in the range 1024..8191 are treated as requiring deactivation.

#### RSS, bit [18]

Range Selector Support. Possible values are:

RSS | Meaning
--- | ---
0b0 | Targeted SGIs with affinity level 0 values of 0 - 15 are supported.
0b1 | Targeted SGIs with affinity level 0 values of 0 - 255 are supported.

This bit is read-only.

#### nDS, bit [17]

Disable Security not supported. Read-only and writes are ignored. Possible values are:

nDS | Meaning
--- | ---
0b0 | The CPU interface logic supports disabling of security.
0b1 | The CPU interface logic does not support disabling of security, and requires that security is not disabled.

#### Bit [16]

Reserved, RES0.

#### A3V, bit [15]

Affinity 3 Valid. Read-only and writes are ignored. Possible values are:

A3V | Meaning
--- | ---
0b0 | The CPU interface logic does not support non-zero values of the Aff3 field in SGI generation System registers.
0b1 | The CPU interface logic supports non-zero values of the Aff3 field in SGI generation System registers.

If EL3 is present, ICC_CTLR.AV3 is an alias of ICC_MCTLR.A3V

#### SEIS, bit [14]

SEI Support. Read-only and writes are ignored. Indicates whether the CPU interface supports generation of SEIs:

SEIS | Meaning
--- | ---
0b0 | The CPU interface logic does not support generation of SEIs.
0b1 | The CPU interface logic supports generation of SEIs.

If EL3 is present, ICC_CTLR.SEIS is an alias of ICC_MCTLR.SEIS

#### IDbits, bits [13:11]

Identifier bits. Read-only and writes are ignored. The number of physical interrupt identifier bits supported:

IDbits | Meaning
--- | ---
0b000 | 16 bits.
0b001 | 24 bits.

All other values are reserved.

If EL3 is present, ICC_CTLR.IDbits is an alias of ICC_MCTLR.IDbits

#### PRIbits, bits [10:8]

Priority bits. Read-only and writes are ignored. The number of priority bits implemented, minus one.

An implementation that supports two Security states must implement at least 32 levels of physical priority (5 priority bits).

An implementation that supports only a single Security state must implement at least 16 levels of physical priority (4 priority bits).

Note

This field always returns the number of priority bits implemented, regardless of the value of SCR.NS or the value of GICD_CTLR.DS.

The division between group priority and subpriority is defined in the binary point registers ICC_BPR0 and ICC_BPR1.

This field determines the minimum value of ICC_BPR0.

#### Bit [7]

Reserved, RES0.

#### PMHE, bit [6]

Priority Mask Hint Enable.

PMHE | Meaning
--- | ---
0b0 | Disables use of the priority mask register as a hint for interrupt distribution.
0b1 | Enables use of the priority mask register as a hint for interrupt distribution.

Software must write ICC_PMR to 0xFF before clearing this field to 0.

An implementation might choose to make this field RAO/WI.

If EL3 is present, ICC_CTLR.PMHE is an alias of ICC_MCTLR.PMHE.

This field resets to 0.

#### RM, bit [5]

SBZ.

The equivalent bit in AArch64 is the Routing Modifier bit. This feature is not supported when EL3 is using AArch32.

This field resets to an architecturally UNKNOWN value.

#### EOImode_EL1NS, bit [4]

EOI mode for interrupts handled at Non-secure EL1 and EL2. Controls whether a write to an End of Interrupt register also deactivates the interrupt:

EOImode_EL1NS | Meaning
--- | ---
0b0 | ICC_EOIR0 and ICC_EOIR1 provide both priority drop and interrupt deactivation functionality. Accesses to ICC_DIR are UNPREDICTABLE.
0b1 | ICC_EOIR0 and ICC_EOIR1 provide priority drop functionality only. ICC_DIR provides interrupt deactivation functionality.

If EL3 is present, ICC_CTLR(NS).EOImode is an alias of ICC_MCTLR.EOImode_EL1NS.

This field resets to an architecturally UNKNOWN value.

#### EOImode_EL1S, bit [3]

EOI mode for interrupts handled at Secure EL1. Controls whether a write to an End of Interrupt register also deactivates the interrupt:

EOImode_EL1S | Meaning
--- | ---
0b0 | ICC_EOIR0 and ICC_EOIR1 provide both priority drop and interrupt deactivation functionality. Accesses to ICC_DIR are UNPREDICTABLE.
0b1 | ICC_EOIR0 and ICC_EOIR1 provide priority drop functionality only. ICC_DIR provides interrupt deactivation functionality.

If EL3 is present, ICC_CTLR(S).EOImode is an alias of ICC_MCTLR.EOImode_EL1S.

This field resets to an architecturally UNKNOWN value.

#### EOImode_EL3, bit [2]

EOI mode for interrupts handled at EL3. Controls whether a write to an End of Interrupt register also deactivates the interrupt:

EOImode_EL3 | Meaning
--- | ---
0b0 | ICC_EOIR0 and ICC_EOIR1 provide both priority drop and interrupt deactivation functionality. Accesses to ICC_DIR are UNPREDICTABLE.
0b1 | ICC_EOIR0 and ICC_EOIR1 provide priority drop functionality only. ICC_DIR provides interrupt deactivation functionality.

This field resets to an architecturally UNKNOWN value.

#### CBPR_EL1NS, bit [1]

Common Binary Point Register, EL1 Non-secure. Controls whether the same register is used for interrupt preemption of both Group 0 and Group 1 Non-secure interrupts at EL1 and EL2:

CBPR_EL1NS | Meaning
--- | ---
0b0 | ICC_BPR0 determines the preemption group for Group 0 interrupts only. ICC_BPR1 determines the preemption group for Non-secure Group 1 interrupts.
0b1 | ICC_BPR0 determines the preemption group for Group 0 interrupts and Non-secure Group 1 interrupts. Non-secure accesses to GICC_BPR and ICC_BPR1 access the state of ICC_BPR0

If EL3 is present, ICC_CTLR(NS).CBPR is an alias of ICC_MCTLR.CBPR_EL1NS.

This field resets to an architecturally UNKNOWN value.

#### CBPR_EL1S, bit [0]

Common Binary Point Register, EL1 Secure. Controls whether the same register is used for interrupt preemption of both Group 0 and Group 1 Secure interrupts in Secure non-Monitor modes:

CBPR_EL1S | Meaning
--- | ---
0b0 | ICC_BPR0 determines the preemption group for Group 0 interrupts only. ICC_BPR1 determines the preemption group for Secure Group 1 interrupts.
0b1 | ICC_BPR0 determines the preemption group for Group 0 interrupts and Secure Group 1 interrupts. Secure EL1 accesses, or EL3 accesses when not in Monitor mode, to ICC_BPR1 access the state of ICC_BPR0.

If EL3 is present, ICC_CTLR(S).CBPR is an alias of ICC_MCTLR.CBPR_EL1S.

This field resets to an architecturally UNKNOWN value.

## Accessing the ICC_MCTLR

This register is only accessible when executing in Monitor mode.

Accesses to this register use the following encodings:

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

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b110 | 0b1100 | 0b1100 | 0b100

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); else UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else return ICC_MCTLR;

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

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b110 | 0b1100 | 0b1100 | 0b100

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); else UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else ICC_MCTLR = 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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