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RNDR, Random Number

The RNDR characteristics are:

Purpose

Random Number. Returns a 64-bit random number which is reseeded from the True Random Number source at an IMPLEMENTATION DEFINED rate.

If the hardware returns a genuine random number, PSTATE.NZCV is set to 0b0000.

If the instruction cannot return a genuine random number in a reasonable period of time, PSTATE.NZCV is set to 0b0100 and the data value returned in UNKNOWN.

Configuration

This register is present only when ARMv8.5-RNG is implemented. Otherwise, direct accesses to RNDR are UNDEFINED.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

RNDR is a 64-bit register.

Field descriptions

The RNDR 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
RNDR
RNDR
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

RNDR, bits [63:0]

Random Number. Returns a 64-bit Random Number which is reseeded from the True Random Number source at an IMPLEMENTATION DEFINED rate.

This field resets to an architecturally UNKNOWN value.

Accessing the RNDR

Accesses to this register use the following encodings:

MRS <Xt>, RNDR

op0	op1	CRn	CRm	op2
0b11	0b011	0b0010	0b0100	0b000

if PSTATE.EL == EL0 then
    return RNDR;
elsif PSTATE.EL == EL1 then
    return RNDR;
elsif PSTATE.EL == EL2 then
    return RNDR;
elsif PSTATE.EL == EL3 then
    return RNDR;

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