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CNTPS_CVAL_EL1, Counter-timer Physical Secure Timer CompareValue register

The CNTPS_CVAL_EL1 characteristics are:

Purpose

Holds the compare value for the secure physical timer, usually accessible at EL3 but configurably accessible at EL1 in Secure state.

Configuration

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

CNTPS_CVAL_EL1 is a 64-bit register.

Field descriptions

The CNTPS_CVAL_EL1 bit assignments are:

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
CompareValue
CompareValue
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

CompareValue, bits [63:0]

Holds the secure physical timer CompareValue.

When CNTPS_CTL_EL1.ENABLE is 1, the timer condition is met when (CNTPCT_EL0 - CompareValue) is greater than or equal to zero. This means that CompareValue acts like a 64-bit upcounter timer. When the timer condition is met:

CNTPS_CTL_EL1.ISTATUS is set to 1.
If CNTPS_CTL_EL1.IMASK is 0, an interrupt is generated.

When CNTPS_CTL_EL1.ENABLE is 0, the timer condition is not met, but CNTPCT_EL0 continues to count.

If the Generic counter is implemented at a size less than 64 bits, then this field is permitted to be implemented at the same width as the counter, and the upper bits are RES0.

The value of this field is treated as zero-extended in all counter calculations.

This field resets to an architecturally UNKNOWN value.

Accessing the CNTPS_CVAL_EL1

Accesses to this register use the following encodings:

MRS <Xt>, CNTPS_CVAL_EL1

op0	op1	CRn	CRm	op2
0b11	0b111	0b1110	0b0010	0b010

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if HaveEL(EL3) && SCR_EL3.NS == '0' then
        if SCR_EL3.EEL2 == '1' then
            UNDEFINED;
        elsif SCR_EL3.ST == '0' then
            AArch64.SystemAccessTrap(EL3, 0x18);
        else
            return CNTPS_CVAL_EL1;
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    return CNTPS_CVAL_EL1;

MSR CNTPS_CVAL_EL1, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b111	0b1110	0b0010	0b010

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if HaveEL(EL3) && SCR_EL3.NS == '0' then
        if SCR_EL3.EEL2 == '1' then
            UNDEFINED;
        elsif SCR_EL3.ST == '0' then
            AArch64.SystemAccessTrap(EL3, 0x18);
        else
            CNTPS_CVAL_EL1 = X[t];
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    CNTPS_CVAL_EL1 = X[t];

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