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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.

RNDR is a read-only register.

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:

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.

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;
              


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