\xcd\x03\x80\xd4\x00\x800\xf8v
Note that non-ascii characters in the above source code will be escaped (such as \x9f).
Disassemble:
ORG 00000H CALL 08003H ;0000 CD 03 80 . . . CALL NC,08000H ;0003 D4 00 80 . . . JR NC,$-6 ;0006 30 F8 0 . HALT ;0008 76 V