code: function rr (cpu, n) {
      const cy = cpu.f >> 4 & 1;
      const r = cy << 7 | n >> 1;
  
      cpu.f = 0;
      if ((r & 0xff) == 0) cpu.f |= FLAG_Z;
      if ((n & 1) != 0) cpu.f |= FLAG_C;
  
      return r;
  }
docs: RR n
  
  Description:
  Rotate n right through Carry flag.
  
  Use with:
  n = A, B, C, D, E, H, L, (HL)
  
  Flags affected:
  Z - Set if result is zero.
  N - Reset.
  H - Reset.
  C - Contains old bit 0 data.
  
  Opcodes:
  Instruction    Parameters    Opcode    Cycles
  RR             A             CB 1F     8
  RR             B             CB 18     8
  RR             C             CB 19     8
  RR             D             CB 1A     8
  RR             E             CB 1B     8
  RR             H             CB 1C     8
  RR             L             CB 1D     8
  RR             (HL)          CB 1E     16