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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 is 0.

RNDR is a read-only register.

Configuration

This register is present only when FEAT_RNG is implemented. Otherwise, direct accesses to RNDR are UNDEFINED.

Attributes

RNDR is a 64-bit register.

Field descriptions

The RNDR bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RNDR
RNDR
313029282726252423222120191817161514131211109876543210

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.

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

Accessing the RNDR

Accesses to this register use the following encodings:

MRS <Xt>, RNDR

op0op1CRnCRmop2
0b110b0110b00100b01000b000
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;