The NIVDM CPU has encoutered an illegal instruction

;3.32---2.循环程序2
;为了简便，按10个数排
DSEG SEGMENT
 DATA DW 56,87,90,96,76,64,47,74,86,95
DSEG ENDS
CSEG SEGMENT
ASSUME CS:CSEG,DS:DSEG
START:
  MOV AX,DSEG
  MOV DS,AX   
  LEA SI,DATA  
  MOV BL,9
NEXT1:
  MOV CL,BL  
NEXT2:
  MOV AX,[SI]
  ADD SI,2
  CMP AX,[SI]
  JNC NEXT3
  MOV DX,[SI]
  MOV [SI],AX
  MOV [SI-2],DX
NEXT3:
  DEC CL
  JNZ NEXT2
  DEC BL
  JNZ NEXT1   
  MOV AH,4CH
  INT 21H         ;返回DOS
CSEG ENDS
END START   
调试时出现 The NIVDM CPU has encoutered an illegal instruction
CS:14B7 IP:000f OP:c4 c6 02 3b 04 Choose 'close' to terminate the application
不知什么原因