DSPSR, Debug Saved Program Status Register

The DSPSR characteristics are:

Purpose

Holds the saved process state for Debug state. On entering Debug state, PSTATE information is written to this register. On exiting Debug state, values are copied from this register to PSTATE.

Configuration

AArch32 System register DSPSR bits [31:0] are architecturally mapped to AArch64 System register DSPSR_EL0[31:0] .

This register is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to DSPSR are UNDEFINED.

Attributes

DSPSR is a 32-bit register.

Field descriptions

The DSPSR bit assignments are:

N, bit [31]

Negative Condition flag. Set to the value of PSTATE.N on entering Debug state, and copied to PSTATE.N on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Z, bit [30]

Zero Condition flag. Set to the value of PSTATE.Z on entering Debug state, and copied to PSTATE.Z on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

C, bit [29]

Carry Condition flag. Set to the value of PSTATE.C on entering Debug state, and copied to PSTATE.C on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

V, bit [28]

Overflow Condition flag. Set to the value of PSTATE.V on entering Debug state, and copied to PSTATE.V on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Q, bit [27]

Overflow or saturation flag. Set to the value of PSTATE.Q on entering Debug state, and copied to PSTATE.Q on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

IT[1:0], bits [26:25]

If-Then. Set to the value of PSTATE.IT[1:0] on entering Debug state, and copied to PSTATE.IT[1:0] on exiting Debug state.

On exiting Debug state DSPSR.IT must contain a value that is valid for the instruction being returned to.

This field resets to an architecturally UNKNOWN value.

DIT, bit [24]

When FEAT_DIT is implemented:

Data Independent Timing. Set to the value of PSTATE.DIT on entering Debug state, and copied to PSTATE.DIT on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

SSBS, bit [23]

When FEAT_SSBS is implemented:

Speculative Store Bypass. Set to the value of PSTATE.SSBS on entering Debug state, and copied to PSTATE.SSBS on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

PAN, bit [22]

When FEAT_PAN is implemented:

Privileged Access Never. Set to the value of PSTATE.PAN on entering Debug state, and copied to PSTATE.PAN on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

SS, bit [21]

Software Step. Set to the value of PSTATE.SS on entering Debug state, and conditionally copied to PSTATE.SS on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

IL, bit [20]

Illegal Execution state. Set to the value of PSTATE.IL on entering Debug state, and copied to PSTATE.IL on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

GE, bits [19:16]

Greater than or Equal flags. Set to the value of PSTATE.GE on entering Debug state, and copied to PSTATE.GE on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

IT[7:2], bits [15:10]

If-Then. Set to the value of PSTATE.IT[7:2] on entering Debug state, and copied to PSTATE.IT[7:2] on exiting Debug state.

DSPSR.IT must contain a value that is valid for the instruction being returned to.

This field resets to an architecturally UNKNOWN value.

E, bit [9]

Endianness. Set to the value of PSTATE.E on entering Debug state, and copied to PSTATE.E on exiting Debug state.

If the implementation does not support big-endian operation, DSPSR.E is RES0. If the implementation does not support little-endian operation, DSPSR.E is RES1. On exiting Debug state, if the implementation does not support big-endian operation at the Exception level being returned to, DSPSR.E is RES0, and if the implementation does not support little-endian operation at the Exception level being returned to, DSPSR.E is RES1.

This field resets to an architecturally UNKNOWN value.

A, bit [8]

SError interrupt mask. Set to the value of PSTATE.A on entering Debug state, and copied to PSTATE.A on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

I, bit [7]

IRQ interrupt mask. Set to the value of PSTATE.I on entering Debug state, and copied to PSTATE.I on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

F, bit [6]

FIQ interrupt mask. Set to the value of PSTATE.F on entering Debug state, and copied to PSTATE.F on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

T, bit [5]

T32 Instruction set state. Set to the value of PSTATE.T on entering Debug state, and copied to PSTATE.T on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

M[4:0], bits [4:0]

Mode. Set to the value of PSTATE.M[4:0] on entering Debug state, and copied to PSTATE.M[4:0] on exiting Debug state.

Other values are reserved. If DSPSR.M[4:0] has a Reserved value, or a value for an unimplemented Exception level, exiting Debug state is an illegal return event, as described in 'Illegal return events from AArch32 state'.

This field resets to an architecturally UNKNOWN value.

if !Halted() then
    UNDEFINED;
else
    return DSPSR;
              

if !Halted() then
    UNDEFINED;
else
    DSPSR = R[t];