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PMCCNTR, Performance Monitors Cycle Count Register

The PMCCNTR characteristics are:

Purpose

Holds the value of the processor Cycle Counter, CCNT, that counts processor clock cycles. See 'Time as measured by the Performance Monitors cycle counter' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile for more information.

PMCCFILTR determines the modes and states in which the PMCCNTR can increment.

Configuration

AArch32 System register PMCCNTR bits [63:0] are architecturally mapped to AArch64 System register PMCCNTR_EL0[63:0] .

AArch32 System register PMCCNTR bits [63:0] are architecturally mapped to External register PMCCNTR_EL0[63:0] .

All counters are subject to any changes in clock frequency, including clock stopping caused by the WFI and WFE instructions. This means that it is CONSTRAINED UNPREDICTABLE whether or not PMCCNTR continues to increment when clocks are stopped by WFI and WFE instructions.

This register is in the Warm reset domain. On a Warm or Cold reset RW fields in this register reset to architecturally UNKNOWN values.

Attributes

PMCCNTR is a 64-bit register that can also be accessed as a 32-bit value. If it is accessed as a 32-bit register, accesses read and write bits [31:0] and do not modify bits [63:32].

Field descriptions

The PMCCNTR bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
CCNT
CCNT
313029282726252423222120191817161514131211109876543210

CCNT, bits [63:0]

Cycle count. Depending on the values of PMCR.{LC,D}, this field increments in one of the following ways:

  • Every processor clock cycle.
  • Every 64th processor clock cycle.

Writing 1 to PMCR.C sets this field to 0.

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

Accessing the PMCCNTR

Accesses to this register use the following encodings:

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

coprocopc1CRnCRmopc2
0b11110b0000b10010b11010b000
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && PMUSERENR_EL0.<CR,EN> == '00' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x03);
        else
            AArch64.AArch32SystemAccessTrap(EL1, 0x03);
    elsif ELUsingAArch32(EL1) && PMUSERENR.<CR,EN> == '00' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x03);
        elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TGE == '1' then
            AArch32.TakeHypTrapException(0x00);
        else
            UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<E2H,TGE> != '11' && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x03);
    else
        return PMCCNTR<31:0>;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x03);
    else
        return PMCCNTR<31:0>;
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x03);
    else
        return PMCCNTR<31:0>;
elsif PSTATE.EL == EL3 then
    return PMCCNTR<31:0>;
              

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

coprocopc1CRnCRmopc2
0b11110b0000b10010b11010b000
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && PMUSERENR_EL0.EN == '0' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x03);
        else
            AArch64.AArch32SystemAccessTrap(EL1, 0x03);
    elsif ELUsingAArch32(EL1) && PMUSERENR.EN == '0' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x03);
        elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TGE == '1' then
            AArch32.TakeHypTrapException(0x00);
        else
            UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<E2H,TGE> != '11' && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x03);
    else
        PMCCNTR = ZeroExtend(R[t]);
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x03);
    else
        PMCCNTR = ZeroExtend(R[t]);
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x03);
    else
        PMCCNTR = ZeroExtend(R[t]);
elsif PSTATE.EL == EL3 then
    PMCCNTR = ZeroExtend(R[t]);
              

MRRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <Rt2>, <CRm>

coprocCRmopc1
0b11110b10010b0000
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && PMUSERENR_EL0.<CR,EN> == '00' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x04);
        else
            AArch64.AArch32SystemAccessTrap(EL1, 0x04);
    elsif ELUsingAArch32(EL1) && PMUSERENR.<CR,EN> == '00' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x04);
        elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TGE == '1' then
            AArch32.TakeHypTrapException(0x00);
        else
            UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<E2H,TGE> != '11' && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x04);
    else
        return PMCCNTR;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x04);
    else
        return PMCCNTR;
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x04);
    else
        return PMCCNTR;
elsif PSTATE.EL == EL3 then
    return PMCCNTR;
              

MCRR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <Rt2>, <CRm>

coprocCRmopc1
0b11110b10010b0000
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && PMUSERENR_EL0.EN == '0' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x04);
        else
            AArch64.AArch32SystemAccessTrap(EL1, 0x04);
    elsif ELUsingAArch32(EL1) && PMUSERENR.EN == '0' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.AArch32SystemAccessTrap(EL2, 0x04);
        elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TGE == '1' then
            AArch32.TakeHypTrapException(0x00);
        else
            UNDEFINED;
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<E2H,TGE> != '11' && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x04);
    else
        PMCCNTR = R[t2]:R[t];
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T9 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T9 == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x04);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HDCR.TPM == '1' then
        AArch32.TakeHypTrapException(0x04);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x04);
    else
        PMCCNTR = R[t2]:R[t];
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.AArch32SystemAccessTrap(EL3, 0x04);
    else
        PMCCNTR = R[t2]:R[t];
elsif PSTATE.EL == EL3 then
    PMCCNTR = R[t2]:R[t];
              


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