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DBGDSCRint, Debug Status and Control Register, Internal View

The DBGDSCRint characteristics are:

Purpose

Main control register for the debug implementation. This is an internal, read-only view.

Configuration

AArch32 System register DBGDSCRint bits [30:29] are architecturally mapped to AArch64 System register MDCCSR_EL0[30:29] .

AArch32 System register DBGDSCRint bits [15:2] are architecturally mapped to AArch32 System register DBGDSCRext[15:2] .

This register is required in all implementations.

DBGDSCRint.{NS, SPNIDdis, SPIDdis, MDBGen, UDCCdis, MOE} are UNKNOWN when the register is accessed at EL0. However, although these values are not accessible at EL0 by instructions that are neither UNPREDICTABLE nor return UNKNOWN values, it is permissible for an implementation to return the values of DBGDSCRext.{NS, SPNIDdis, SPIDdis, MDBGen, UDCCdis, MOE} for these fields at EL0.

It is also permissible for an implementation to return the same values as defined for a read of DBGDSCRint at EL1 or above. (This is the case even if the implementation does not support AArch32 at EL1 or above.)

Attributes

DBGDSCRint is a 32-bit register.

Field descriptions

The DBGDSCRint bit assignments are:

313029282726252423222120191817161514131211109876543210
RES0RXfullTXfullRES0NSSPNIDdisSPIDdisMDBGenRES0UDCCdisRES0MOERES0

Bit [31]

Reserved, RES0.

RXfull, bit [30]

DTRRX full. Read-only view of the equivalent bit in the EDSCR.

TXfull, bit [29]

DTRTX full. Read-only view of the equivalent bit in the EDSCR.

Bits [28:19]

Reserved, RES0.

NS, bit [18]

Non-secure status.

Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.

SPNIDdis, bit [17]

Secure privileged non-invasive debug disable.

Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.

SPIDdis, bit [16]

Secure privileged invasive debug disable.

Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.

MDBGen, bit [15]

Monitor debug events enable.

Read-only view of the equivalent bit in the DBGDSCRext.

Bits [14:13]

Reserved, RES0.

UDCCdis, bit [12]

User mode access to Debug Communications Channel disable.

Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.

Bits [11:6]

Reserved, RES0.

MOE, bits [5:2]

Method of Entry for debug exception. When a debug exception is taken to an Exception level using AArch32, this field is set to indicate the event that caused the exception:

MOEMeaning
0b0001

Breakpoint

0b0011

Software breakpoint (BKPT) instruction

0b0101

Vector catch

0b1010

Watchpoint

Read-only view of the equivalent bit in the DBGDSCRext.

Bits [1:0]

Reserved, RES0.

Accessing the DBGDSCRint

Accesses to this register use the following encodings:

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

coprocopc1CRnCRmopc2
0b11100b0000b00000b00010b000
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && MDSCR_EL1.TDCC == '1' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x05);
        else
            AArch64.AArch32SystemAccessTrap(EL1, 0x05);
    elsif ELUsingAArch32(EL1) && DBGDSCRext.UDCCdis == '1' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x05);
        elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TGE == '1' then
            AArch32.TakeHypTrapException(0x00);
        else
            UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && (HCR_EL2.TGE == '1' || MDCR_EL2.<TDE,TDA> != '00') then
        AArch64.AArch32SystemAccessTrap(EL2, 0x05);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x05);
    else
        return DBGDSCRint;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.<TDE,TDA> != '00' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x05);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.<TDE,TDA> != '00' then
        AArch32.TakeHypTrapException(0x05);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x05);
    else
        return DBGDSCRint;
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x05);
    else
        return DBGDSCRint;
elsif PSTATE.EL == EL3 then
    return DBGDSCRint;
              


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