code: def instruction_RTI(self, opcode):
          
          cc = self.pull_byte(self.system_stack_pointer) # CC
          self.set_cc(cc)
          if self.E:
              self.accu_a.set(
                  self.pull_byte(self.system_stack_pointer) # A
              )
              self.accu_b.set(
                  self.pull_byte(self.system_stack_pointer) # B
              )
              self.direct_page.set(
                  self.pull_byte(self.system_stack_pointer) # DP
              )
              self.index_x.set(
                  self.pull_word(self.system_stack_pointer) # X
              )
              self.index_y.set(
                  self.pull_word(self.system_stack_pointer) # Y
              )
              self.user_stack_pointer.set(
                  self.pull_word(self.system_stack_pointer) # U
              )
  
          self.program_counter.set(
              self.pull_word(self.system_stack_pointer) # PC
          )
docs: The saved machine state is recovered from the hardware stack and control
          is returned to the interrupted program. If the recovered E (entire) bit
          is clear, it indicates that only a subset of the machine state was saved
          (return address and condition codes) and only that subset is recovered.
  
          source code forms: RTI
  
          CC bits "HNZVC": -----