i think this is compiler bug in keil c51 i cheak this code in compiler 6.20
it work good but in c51 ver 7.01 have bug !

compiler and linker directive :
ROM(COMPACT) OPTIMIZE (7,SPEED) REGFILE (.polaro01.ORC) BROWSE NOINTPROMOTE DEBUG OBJECTEXTEND TABS (2)
TO "polaro01" REGFILE (.polaro01.ORC) RAMSIZE(256) DISABLEWARNING (15,16)



static void serial () small interrupt SIO_VECTOR using 2 {
register char buf;
if (RI0 != 0){
RI0 = 0;
buf = SBUF0 ;
if (buf == 0x12){
//some code
return; <---error line code !
}
if (inpack){
//some code
return;
}
if (buf == ESC) {
//some code
return;
}
//some code
return;
}//end inpack
if (!StartSPack && !InSPack) return;
//some code jamp to ersp
}
else if (buf != *(SDPointer -1)) goto ERSP;
if (buf == 0x66){
//some code
return; //end of good send;
}
if (!*SDPointer){
outchar(0x14);
return;
}
outchar(*SDPointer);
SDPointer++;
return;
//--------------- send ERROR Routine
ERSP:
outchar(ESC);
InSPack = 0;
StartSPack = 0;
return;
//------------------ti
}
if (TI0 != 0){
TI0 = 0 ;
TI_E = 0;
}
}


very nice bug in on return line jamp to ersp to end of interrupt ! you can see this src in keil


; PackState = 1; //inpack = 1;
; SOURCE LINE # 61
MOV PackState,#01H
; SOURCE LINE # 63
; StartSPack = 0;
; SOURCE LINE # 64
AJMP ?C0028
; //


the address of ?C0028 :

?C0028:
CLR InSPack
; StartSPack = 0;
; SOURCE LINE # 112
CLR StartSPack
SJMP ?C0008
; return;


this is not end or exit point of my code this is one jmp in middle of my code !
the address of exit of my code is SJMP ?C0008

?C0008:
POP PSW
POP DPL
POP DPH
POP B
POP ACC
RETI
; END OF serial


i try this code compile in ver 6.21 6.20c and some other ver good but in 7.01 :-(