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FCSEIDR, FCSE Process ID register

The FCSEIDR characteristics are:

Purpose

Identifies whether the Fast Context Switch Extension (FCSE) is implemented.

From Armv8, the FCSE is not implemented, so this register is RAZ/WI. Software can access this register to determine that the implementation does not include the FCSE.

Configuration

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

Attributes

FCSEIDR is a 32-bit register.

Field descriptions

The FCSEIDR bit assignments are:

313029282726252423222120191817161514131211109876543210
RAZ/WI

Bits [31:0]

Reserved, RAZ/WI.

Accessing the FCSEIDR

Accesses to this register use the following encodings:

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

coprocopc1CRnCRmopc2
0b11110b0000b11010b00000b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T13 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T13 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        return FCSEIDR;
elsif PSTATE.EL == EL2 then
    return FCSEIDR;
elsif PSTATE.EL == EL3 then
    return FCSEIDR;
              

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

coprocopc1CRnCRmopc2
0b11110b0000b11010b00000b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T13 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T13 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        FCSEIDR = R[t];
elsif PSTATE.EL == EL2 then
    FCSEIDR = R[t];
elsif PSTATE.EL == EL3 then
    FCSEIDR = R[t];