;XOR starting from start_addr for bytes length and compare with 0xaabbbbaa
; input r0,r1 for example  0x20000, 0xe0000
;f_0x290(start_addr,bytes)
;{
;  r4 = bytes/4;
;  r2 = 0;
;  r3 = 0;
;  ip = start_addr;
;  while(r2<r4){
;	r3 ^= *(ip);
;	ip += 4;
;	r2++;
;   }
;   if(r3==0xaabbbbaa)
;	return 0;
;   else
;	return -1;
;}
;
00000290 <F21_0x290>:
     290:	e92d0010 	stmdb	sp!, {r4}
     294:	e3a03000 	mov	r3, #0	; 0x0
     298:	e1a04121 	mov	r4, r1, lsr #2
     29c:	e1a0c000 	mov	ip, r0
     2a0:	e3a02000 	mov	r2, #0	; 0x0
     2a4:	ea000003 	b	2b8 <L15_0x2B8>

000002a8 <L16_0x2A8>:
     2a8:	e59c0000 	ldr	r0, [ip]
     2ac:	e0233000 	eor	r3, r3, r0
     2b0:	e28cc004 	add	ip, ip, #4	; 0x4
     2b4:	e2822001 	add	r2, r2, #1	; 0x1

000002b8 <L15_0x2B8>:
     2b8:	e1520004 	cmp	r2, r4
     2bc:	bafffff9 	blt	2a8 <L16_0x2A8>
     2c0:	e59f00fc 	ldr	r0, [pc, #252]	; 3c4 (0xaabbbbaa) 
     2c4:	e1530000 	cmp	r3, r0
     2c8:	0a000001 	beq	2d4 <L17_0x2D4>
     2cc:	e3e00000 	mvn	r0, #0	; 0x0
     2d0:	ea000000 	b	2d8 <L18_0x2D8>

000002d4 <L17_0x2D4>:
     2d4:	e3a00000 	mov	r0, #0	; 0x0

000002d8 <L18_0x2D8>:
     2d8:	e8bd0010 	ldmia	sp!, {r4}
     2dc:	e12fff1e 	bx	lr