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MDRAR_EL1, Monitor Debug ROM Address Register

The MDRAR_EL1 characteristics are:

Purpose

Defines the base physical address of a 4KB-aligned memory-mapped debug component, usually a ROM table that locates and describes the memory-mapped debug components in the system. Armv8 deprecates any use of this register.

Configuration

AArch64 System register MDRAR_EL1 bits [63:0] are architecturally mapped to AArch32 System register DBGDRAR[63:0] .

Attributes

MDRAR_EL1 is a 64-bit register.

Field descriptions

The MDRAR_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0ROMADDR[51:48]ROMADDR[47:12]
ROMADDR[47:12]RES0Valid
313029282726252423222120191817161514131211109876543210

Bits [63:52]

Reserved, RES0.

ROMADDR[51:48], bits [51:48]

When ARMv8.2-LPA is implemented:

Extension to ROMADDR[47:12]. See ROMADDR[47:12] for more details.


Otherwise:

Reserved, RES0.

ROMADDR[47:12], bits [47:12]

Bits[47:12] of the ROM table physical address.

When ARMv8.2-LPA is implemented, ROMADDR[51:48] forms the upper part of the address value. Otherwise, ROMADDR[51:48] is RES0.

If the physical address size in bits (PAsize) is less than 52, then the register bits corresponding to ROMADDR [51:PAsize] are RES0.

Bits [11:0] of the ROM table physical address are zero.

Arm strongly recommends that bits ROMADDR[(PAsize-1):32] are zero in any system that supports AArch32 at the highest implemented Exception level.

In an implementation that includes EL3, ROMADDR is an address in Non-secure memory. It is IMPLEMENTATION DEFINED whether the ROM table is also accessible in Secure memory.

Bits [11:2]

Reserved, RES0.

Valid, bits [1:0]

This field indicates whether the ROM Table address is valid.

ValidMeaning
0b00

ROM Table address is not valid. Software must ignore ROMADDR.

0b11

ROM Table address is valid.

Other values are reserved.

Accessing the MDRAR_EL1

Accesses to this register use the following encodings:

MRS <Xt>, MDRAR_EL1

op0op1CRnCRmop2
0b100b0000b00010b00000b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then
        UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.<TDE,TDRA> != '00' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return MDRAR_EL1;
elsif PSTATE.EL == EL2 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then
        UNDEFINED;
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return MDRAR_EL1;
elsif PSTATE.EL == EL3 then
    return MDRAR_EL1;