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Memory Model Feature Register 0

The ID_MMFR0 characteristics are:

Purpose

Provides information about the memory model and memory management support in AArch32.

Usage constraints

This register is accessible as follows:

EL0

(NS)

EL0

(S)

EL1

(NS)

EL1

(S)

EL2

EL3

(SCR.NS = 1)

EL3

(SCR.NS = 0)

- - RO RO RO RO RO

Must be interpreted with ID_MMFR1, ID_MMFR2, and ID_MMFR3. See:

Configurations

ID_MMFR0 is architecturally mapped to AArch64 register ID_MMFR0_EL1.

There is one copy of this register that is used in both Secure and Non-secure states.

Attributes

ID_MMFR0 is a 32-bit register.

Figure 4.82 shows the ID_MMFR0 bit assignments.

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Table 4.170 shows the ID_MMFR0 bit assignments.

Table 4.170. ID_MMFR0 bit assignments
Bits Name Function
[31:28] InnerShr

Indicates the innermost shareability domain implemented:

0x1

Implemented with hardware coherency support.

[27:24] FCSE

Indicates support for Fast Context Switch Extension (FCSE):

0x0

Not supported.

[23:20] AuxReg

Indicates support for Auxiliary registers:

0x2

Support for Auxiliary Fault Status Registers (AIFSR and ADFSR) and Auxiliary Control Register.

[19:16] TCM

Indicates support for TCMs and associated DMAs:

0x0

Not supported.

[15:12] ShareLvl

Indicates the number of shareability levels implemented:

0x1

Two levels of shareability implemented.

[11:8] OuterShr

Indicates the outermost shareability domain implemented:

0x1

Implemented with hardware coherency support.

[7:4] PMSA

Indicates support for a Protected Memory System Architecture (PMSA):

0x0

Not supported.

[3:0] VMSA

Indicates support for a Virtual Memory System Architecture (VMSA).

0x5

Support for:

  • VMSAv7, with support for remapping and the Access flag.

  • The PXN bit in the Short-descriptor translation table format descriptors.

  • The Long-descriptor translation table format.


To access the ID_MMFR0:

	
MRC p15,0,<Rt>,c0,c1,4 ; Read ID_MMFR0 into Rt

Register access is encoded as follows:

Table 4.171. ID_MMFR0 access encoding
coproc opc1 CRn CRm opc2
1111 000 0000 0001 100

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