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# DBGDSCRext, Debug Status and Control Register, External View

The DBGDSCRext characteristics are:

## Purpose

Main control register for the debug implementation.

## Configuration

AArch32 System register DBGDSCRext bits [31:0] are architecturally mapped to AArch64 System register MDSCR_EL1[31:0].

AArch32 System register DBGDSCRext bit [15] is architecturally mapped to AArch32 System register DBGDSCRint[15].

AArch32 System register DBGDSCRext bit [12] is architecturally mapped to AArch32 System register DBGDSCRint[12].

AArch32 System register DBGDSCRext bits [5:2] are architecturally mapped to AArch32 System register DBGDSCRint[5:2].

This register is present only when EL1 is capable of using AArch32. Otherwise, direct accesses to DBGDSCRext are UNDEFINED.

This register is required in all implementations.

## Attributes

DBGDSCRext is a 32-bit register.

## Field descriptions

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
TFO | RXfull | TXfull | RES0 | RXO | TXU | RES0 | INTdis | TDA | RES0 | SC2 | NS | SPNIDdis | SPIDdis | MDBGen | HDE | RES0 | UDCCdis | RES0 | ERR | MOE | RES0

#### TFO, bit [31]
When FEAT_TRF is implemented:

Trace Filter override. Used for save/restore of EDSCR.TFO.

When the OS Lock is unlocked, DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When the OS Lock is locked, DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.TFO. Reads and writes of this bit are indirect accesses to EDSCR.TFO.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

####
Otherwise:

Reserved, RES0.

#### RXfull, bit [30]

DTRRX full. Used for save/restore of EDSCR.RXfull.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.RXfull. Reads and writes of this bit are indirect accesses to EDSCR.RXfull.

Arm deprecates use of this bit other than for save/restore. Use DBGDSCRint to access the DTRRX full status.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### TXfull, bit [29]

DTRTX full. Used for save/restore of EDSCR.TXfull.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.TXfull. Reads and writes of this bit are indirect accesses to EDSCR.TXfull.

Arm deprecates use of this bit other than for save/restore. Use DBGDSCRint to access the DTRTX full status.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### Bit [28]

Reserved, RES0.

#### RXO, bit [27]

Used for save/restore of EDSCR.RXO.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.RXO. Reads and writes of this bit are indirect accesses to EDSCR.RXO.

When DBGOSLSR.OSLK == 1, if bits [27,6] of the value written to DBGDSCRext are {1,0}, that is, the RXO bit is 1 and the ERR bit is 0, the PE sets EDSCR.{RXO,ERR} to UNKNOWN values.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### TXU, bit [26]

Used for save/restore of EDSCR.TXU.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.TXU. Reads and writes of this bit are indirect accesses to EDSCR.TXU.

When DBGOSLSR.OSLK == 1, if bits [26,6] of the value written to DBGDSCRext are {1,0}, that is, the TXU bit is 1 and the ERR bit is 0, the PE sets EDSCR.{TXU,ERR} to UNKNOWN values.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### Bits [25:24]

Reserved, RES0.

#### INTdis, bits [23:22]

Used for save/restore of EDSCR.INTdis.

When DBGOSLSR.OSLK == 0, this field is RO, and software must treat it as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this field is RW and holds the value of EDSCR.INTdis. Reads and writes of this field are indirect accesses to EDSCR.INTdis.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### TDA, bit [21]

Used for save/restore of EDSCR.TDA.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.TDA. Reads and writes of this bit are indirect accesses to EDSCR.TDA.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### Bit [20]

Reserved, RES0.

#### SC2, bit [19]
When FEAT_PCSRv8 is implemented, FEAT_VHE is implemented and FEAT_PCSRv8p2 is not implemented:

Used for save/restore of EDSCR.SC2.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.SC2. Reads and writes of this bit are indirect accesses to EDSCR.SC2.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

####
Otherwise:

Reserved, RES0.

#### NS, bit [18]

Non-secure status.

Arm deprecates use of this field.

NS | Meaning
--- | ---
0b0 | Secure state.
0b1 | Non-secure state.

Access to this field is RO.

#### SPNIDdis, bit [17]
When EL3 is implemented:

Secure privileged profiling disabled status bit.

SPNIDdis | Meaning
--- | ---
0b0 | Profiling allowed in Secure privileged modes.
0b1 | Profiling prohibited in Secure privileged modes.

This field reads as 0 if any of the following applies, and reads as 1 otherwise:

- FEAT_Debugv8p2 is not implemented and ExternalSecureNoninvasiveDebugEnabled() returns TRUE.
- EL3 is using AArch32 and the value of SDCR.SPME is 1.
- EL3 is using AArch64 and the value of MDCR_EL3.SPME is 1.

Arm deprecates use of this field.

Access to this field is RO.

####
Otherwise:

Reserved, RES0.

#### SPIDdis, bit [16]
When EL3 is implemented:

Secure privileged AArch32 invasive self-hosted debug disabled status bit. The value of this bit depends on the value of SDCR.SPD and the pseudocode function AArch32.SelfHostedSecurePrivilegedInvasiveDebugEnabled().

SPIDdis | Meaning
--- | ---
0b0 | Self-hosted debug enabled in Secure privileged AArch32 modes.
0b1 | Self-hosted debug disabled in Secure privileged AArch32 modes.

This bit reads as 1 if any of the following is true and reads as 0 otherwise:

- EL3 is using AArch32 and SDCR.SPD has the value 0b10.
- EL3 is using AArch64 and MDCR_EL3.SPD32 has the value 0b10.
- EL3 is using AArch32, SDCR.SPD has the value 0b00, and AArch32.SelfHostedSecurePrivilegedInvasiveDebugEnabled() returns FALSE.
- EL3 is using AArch64, MDCR_EL3.SPD32 has the value 0b00, and AArch32.SelfHostedSecurePrivilegedInvasiveDebugEnabled() returns FALSE.

Arm deprecates use of this field.

Access to this field is RO.

####
Otherwise:

Reserved, RES0.

#### MDBGen, bit [15]

Monitor debug events enable. Enable Breakpoint, Watchpoint, and Vector Catch exceptions.

MDBGen | Meaning
--- | ---
0b0 | Breakpoint, Watchpoint, and Vector Catch exceptions disabled.
0b1 | Breakpoint, Watchpoint, and Vector Catch exceptions enabled.

The reset behavior of this field is:

- On a Warm reset, this field resets to 0.

#### HDE, bit [14]

Used for save/restore of EDSCR.HDE.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.HDE. Reads and writes of this bit are indirect accesses to EDSCR.HDE.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### Bit [13]

Reserved, RES0.

#### UDCCdis, bit [12]

Traps EL0 accesses to the DCC registers to Undefined mode.

UDCCdis | Meaning
--- | ---
0b0 | This control does not cause any instructions to be trapped.
0b1 | EL0 accesses to the DBGDSCRint, DBGDTRRXint, DBGDTRTXint, DBGDIDR, DBGDSAR, and DBGDRAR are trapped to Undefined mode.

Note

All accesses to these registers are trapped, including LDC and STC accesses to DBGDTRTXint and DBGDTRRXint, and MRRC accesses to DBGDSAR and DBGDRAR.

Traps of EL0 accesses to the DBGDTRRXint and DBGDTRTXint are ignored in Debug state.

The reset behavior of this field is:

- On a Warm reset, this field resets to 0.

#### Bits [11:7]

Reserved, RES0.

#### ERR, bit [6]

Used for save/restore of EDSCR.ERR.

When DBGOSLSR.OSLK == 0, software must treat this bit as UNK/SBZP.

When DBGOSLSR.OSLK == 1, this bit holds the value of EDSCR.ERR. Reads and writes of this bit are indirect accesses to EDSCR.ERR.

The architected behavior of this field determines the value it returns after a reset.

Accessing this field has the following behavior:

- When DBGOSLSR.OSLK == 1, access to this field is RW.
- When DBGOSLSR.OSLK == 0, access to this field is RO.

#### 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:

MOE | Meaning
--- | ---
0b0001 | Breakpoint.
0b0011 | Software breakpoint (BKPT) instruction.
0b0101 | Vector catch.
0b1010 | Watchpoint.

The reset behavior of this field is:

- On a Warm reset, this field resets to an architecturally UNKNOWN value.

#### Bits [1:0]

Reserved, RES0.

## Accessing DBGDSCRext

Individual fields within this register might have restricted accessibility when the OS Lock is unlocked, DBGOSLSR.OSLK == 0. See the field descriptions for more detail.

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

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

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1110 | 0b000 | 0b0000 | 0b0010 | 0b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then UNDEFINED; elsif 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 if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); else R[t] = DBGDSCRext; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then UNDEFINED; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); else R[t] = DBGDSCRext; elsif PSTATE.EL == EL3 then R[t] = DBGDSCRext;

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

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1110 | 0b000 | 0b0000 | 0b0010 | 0b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then UNDEFINED; elsif 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 if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); else DBGDSCRext = R[t]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then UNDEFINED; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); else DBGDSCRext = R[t]; elsif PSTATE.EL == EL3 then DBGDSCRext = 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

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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