\xfb\xcd\x03\x800\x01v\xa6\xe5
Note that non-ascii characters in the above source code will be escaped (such as \x9f).
Disassemble:
ORG 00000H EI ;0000 FB . CALL 08003H ;0001 CD 03 80 . . . JR NC,$+3 ;0004 30 01 0 . HALT ;0006 76 V AND (HL) ;0007 A6 . PUSH HL ;0008 E5 .