Main control register for the debug implementation. This is an internal, read-only view.
AArch32 System register DBGDSCRint bits [30:29] are architecturally mapped to AArch64 System register MDCCSR_EL0[30:29].
AArch32 System register DBGDSCRint bit [15] is architecturally mapped to AArch64 System register MDSCR_EL1[15].
AArch32 System register DBGDSCRint bit [12] is architecturally mapped to AArch64 System register MDSCR_EL1[12].
AArch32 System register DBGDSCRint bits [5:2] are architecturally mapped to AArch64 System register MDSCR_EL1[5:2].
AArch32 System register DBGDSCRint bit [15] is architecturally mapped to AArch32 System register DBGDSCRext[15].
AArch32 System register DBGDSCRint bit [12] is architecturally mapped to AArch32 System register DBGDSCRext[12].
AArch32 System register DBGDSCRint bits [5:2] are architecturally mapped to AArch32 System register DBGDSCRext[5:2].
This register is present only when AArch32 is supported. Otherwise, direct accesses to DBGDSCRint are UNDEFINED.
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.)
DBGDSCRint is a 32-bit register.
| 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 | RXfull | TXfull | RES0 | NS | SPNIDdis | SPIDdis | MDBGen | RES0 | UDCCdis | RES0 | MOE | RES0 | |||||||||||||||||||
Reserved, RES0.
DTRRX full. Read-only view of the equivalent bit in the EDSCR.
DTRTX full. Read-only view of the equivalent bit in the EDSCR.
Reserved, RES0.
Non-secure status.
Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.
Secure privileged non-invasive debug disable.
Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.
Secure privileged invasive debug disable.
Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.
Monitor debug events enable.
Read-only view of the equivalent bit in the DBGDSCRext.
Reserved, RES0.
User mode access to Debug Communications Channel disable.
Read-only view of the equivalent bit in the DBGDSCRext. Arm deprecates use of this field.
Reserved, RES0.
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 |
Read-only view of the equivalent bit in the DBGDSCRext.
Reserved, RES0.
When <Rt> is APSR_nzcv, encoded as R15, then instead of reading the entire register, the access copies DBGDSCRint[31:28] into the PSTATE NZCV flags.
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 | 0b0001 | 0b000 |
if Halted() && ConstrainUnpredictableBool(Unpredictable_IGNORETRAPINDEBUG) then if t == 15 then ConstrainUnpredictableProcedure(Unpredictable_MRC_APSR_TARGET); else R[t] = DBGDSCRint; elsif PSTATE.EL == EL0 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDCC == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && ELUsingAArch32(EL3) && SDCR.TDCC == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then UNDEFINED; elsif !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) && MDCR_EL2.TDCC == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x05); elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TDCC == '1' then AArch32.TakeHypTrapException(0x05); elsif EL2Enabled() && !ELUsingAArch32(EL2) && (HCR_EL2.TGE == '1' || MDCR_EL2.<TDE,TDA> != '00') then AArch64.AArch32SystemAccessTrap(EL2, 0x05); elsif EL2Enabled() && ELUsingAArch32(EL2) && (HCR.TGE == '1' || HDCR.<TDE,TDA> != '00') then AArch32.TakeHypTrapException(0x05); elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDCC == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SDCR.TDCC == '1' then if EL3SDDUndef() then UNDEFINED; else AArch32.TakeMonitorTrapException(); elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); else if t == 15 then if Halted() then ConstrainUnpredictableProcedure(Unpredictable_MRC_APSR_TARGET); else PSTATE.<N,Z,C,V> = DBGDSCRint<31:28>; else R[t] = DBGDSCRint; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDCC == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && ELUsingAArch32(EL3) && SDCR.TDCC == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TDCC == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x05); elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TDCC == '1' then AArch32.TakeHypTrapException(0x05); 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.TDCC == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SDCR.TDCC == '1' then if EL3SDDUndef() then UNDEFINED; else AArch32.TakeMonitorTrapException(); elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); else if t == 15 then if Halted() then ConstrainUnpredictableProcedure(Unpredictable_MRC_APSR_TARGET); else PSTATE.<N,Z,C,V> = DBGDSCRint<31:28>; else R[t] = DBGDSCRint; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDCC == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && ELUsingAArch32(EL3) && SDCR.TDCC == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then UNDEFINED; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDCC == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SDCR.TDCC == '1' then if EL3SDDUndef() then UNDEFINED; else AArch32.TakeMonitorTrapException(); elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TDA == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x05); else if t == 15 then if Halted() then ConstrainUnpredictableProcedure(Unpredictable_MRC_APSR_TARGET); else PSTATE.<N,Z,C,V> = DBGDSCRint<31:28>; else R[t] = DBGDSCRint; elsif PSTATE.EL == EL3 then if PSTATE.M != M32_Monitor && SDCR.TDCC == '1' then AArch32.TakeMonitorTrapException(); else if t == 15 then if Halted() then ConstrainUnpredictableProcedure(Unpredictable_MRC_APSR_TARGET); else PSTATE.<N,Z,C,V> = DBGDSCRint<31:28>; else R[t] = DBGDSCRint;