汇编语言当AX=008FH的时候用CMP AL,0和JNL NEXT语句为什么不进行跳转？但是用小于这个数字就可以

这是一个求根号的程序   利用1+3+5+7+9=25=5^2这个原理，当求144以上时出错
CRLF MACRO
        MOV     DL,0DH
        MOV     AH,02H
        INT     21H
        MOV     DL,0AH
        MOV     AH,02H
        INT     21H
      ENDM

DATA SEGMENT
DATA1   DB      'Input the number!','$'
DATA2   DB      'The answer is:','$'
MID	DB	-1
NUM     DB      20
        DB      ?
        DB      20 DUP(?)
TEN     DB      10
RESULT	DB	20 DUP(?)
DATA ENDS

STACK SEGMENT
STA     DW      256 DUP(?)
TOP	EQU	LENGTH STA
STACK ENDS

CODE SEGMENT
        ASSUME  CS:CODE,DS:DATA,SS:STACK
START:  MOV     AX,DATA
        MOV     DS,AX

        LEA     DX,DATA1		;显示输入数字
        MOV     AH,9
        INT     21H
	LEA     DX,NUM			;输入数字
        MOV     AH,10
        INT     21H
        CRLF

        LEA     BX,NUM
	MOV	SI,0
	MOV	CX,0
        ADD     BX,02H
BCD:    SUB     DS:[BX+SI],byte ptr 30H	;ASCII变非压缩BCD码
        INC     SI
	INC	CX
        CMP     DS:[BX+SI],byte ptr 0DH
        JNE     BCD
	MOV	SI,0
        MOV     AX,0
HEX:    MUL     TEN                      
        ADD     AL,DS:[BX+SI]
	INC	SI
	LOOP	HEX

	LEA	BX,MID
        MOV     CX,0FFH            
NEXT:   ADD     DS:[BX],BYTE PTR 02H             ;开方运算，结果送CX
        SUB     AL,DS:[BX]
	INC	CX
        CMP     AL,0
	JGE	NEXT                 ；！！！就是这里！！！
	
	LEA	DX,DATA2		;显示结果
	MOV	AH,9
	INT	21H
        MOV     AL,CL
        MOV     AH,0
	LEA	BX,RESULT
	MOV	SI,0
ASCII:	DIV     TEN			;数字变ASCII码
	ADD	AH,30H
	MOV	DS:[BX+SI],AH
	INC	SI
	MOV	AH,0
	CMP	AL,0
	JG	ASCII
DISPLAY:MOV	DL,DS:[BX+SI]
	MOV	AH,2
	INT	21H
	DEC	SI
	CMP	SI,0
	JGE	DISPLAY	
	MOV	AX,4C00H
	INT	21H
CODE ENDS
	END START