assembly : adding label to dissasembled code

Thread Starter

furtsiv

Joined Mar 7, 2017
16
hi there community
i would like to create a 8051 hex from a previous hex file
i dissembled the hex then i wanted to add some personal code to the begining

but the original hex have some LJMP and ACALL instructions wich jump to specified adress
but if i add my personal code then original code addresses must be changed to new values.
is there an application that can convert for example
ACALL 0120H
to
ACALL label1 (then add this label1 to the address 0120H)
this way code will jump to specified label instead of wrong address .

my personal code :
MOV A,#0
MOV DPTR,#4000H
MOVX A,@DPTR
MOV R0,A
DJNZ R0,AGAIN
MOV 0C7H,#0AAH
MOV 0C7H,#055H
ORL 087H,#02h

AGAIN: MOV A,#0
MOV A,R0
MOVX @DPTR,A

and this is the beginning of original hex

LJMP 002CH
RETI
NOP
NOP
NOP
NOP
NOP
NOP
NOP
LJMP 0650H
RETI
NOP
NOP
NOP
NOP
RETI
NOP
NOP
NOP
NOP
NOP
NOP
NOP
RETI
NOP
NOP
NOP
NOP
NOP
NOP
NOP
RETI
NOP
NOP
NOP
NOP
NOP
NOP
NOP
RETI
LCALL 0819H
CLR 4CH
MOV DPTR,#1800H
MOV A,#0AAH
MOVX @DPTR,A
INC DPTR
MOV A,#0A5H
MOVX @DPTR,A
MOV DPTR,#1809H
MOV A,#0F0H
MOVX @DPTR,A
MOV DPTR,#1808H
 
Last edited:

LesJones

Joined Jan 8, 2017
3,640
It looks like it was not a very good disassembler that was used. Disassemblers that I have used have allways put the labels on the left hand side so you know where the jump or call goes to in the disassembler listing. You may have to do this by hand. I think you will have to look at the memory locations in the HEX file and try to match up a few instructions either side of the location with the disassembler listing. I may be better to try to find a better disassembler program.

Les.
 

Thread Starter

furtsiv

Joined Mar 7, 2017
16
It looks like it was not a very good disassembler that was used. Disassemblers that I have used have allways put the labels on the left hand side so you know where the jump or call goes to in the disassembler listing. You may have to do this by hand. I think you will have to look at the memory locations in the HEX file and try to match up a few instructions either side of the location with the disassembler listing. I may be better to try to find a better disassembler program.

Les.
thanks for the advise
i used a better disassembler and now i have labels ,but when i implement my code first then add dissambled code and compile it i get it to work only if my personal code is less than 5 instructions ,if i insert more instructions final hex will not work
for example this works :

MOV A,#02H
MOV A,#03H
MOV A,#0
// disassembled code here //

this will not work:
MOV A,#01H
MOV A,#04H
MOV A,#08H
MOV A,#02H
MOV A,#03H
MOV A,#0
// disassembled code here //


the new disassembler code is like this :
ljmp X002c
;
reti
;
NOP
NOP
NOP
NOP
NOP
NOP
NOP
;
ljmp X0650
;
reti
;
NOP
NOP
NOP
NOP
;
reti
;
NOP
NOP
NOP
NOP
NOP
NOP
NOP
;
reti
;
NOP
NOP
NOP
NOP
NOP
NOP
NOP
;
reti
;
NOP
NOP
NOP
NOP
NOP
NOP
NOP
;
reti
;
X002c: lcall X0819
clr 29h.4
mov dptr,#X1800
mov a,#0aah
movx @dptr,a
inc dptr
mov a,#0a5h
movx @dptr,a
mov dptr,#X1809
mov a,#0f0h
movx @dptr,a
mov dptr,#X1808
mov a,#0
movx @dptr,a
mov r2,#10h
X0049: mov dph,#0bbh
mov a,#9bh
movx @dptr,a
mov a,#0
lcall X0464
djnz r2,X0049
mov 3eh,#0ffh
mov 62h,#80h
mov 63h,#0
mov 61h,#8
mov 64h,#0
setb 29h.0
mov 3ah,#50h
mov 55h,#0ah
setb 2fh.4
setb 2fh.5
setb 2fh.0
setb 2fh.1
setb 2fh.2
setb 2fh.3
mov 44h,#80h
mov 45h,#80h
mov 30h,#80h
mov 31h,#80h
mov 40h,#80h
mov 41h,#80h
mov 74h,#80h
mov 75h,#80h
mov 70h,#80h
mov 71h,#80h
mov 72h,#80h
mov 73h,#80h
clr 2ah.0
clr 2ah.1
clr 2ah.2
clr 2ah.4
clr 2ah.5
clr 2fh.6
clr 29h.2
mov 6ah,#50h
mov 37h,#80h
mov 38h,#8
mov 2dh,#0ffh
mov 2ch,#0ffh
mov 2bh,#0ffh
mov a,#0
lcall X0464
mov 2dh,#0ffh
mov 2ch,#0ffh
mov 2bh,#0ffh
clr 29h.2
mov 6ah,#50h
mov 68h,#0ffh
mov 67h,#0ffh
mov 69h,#0ffh
mov 30h,#0ffh
mov 70h,#0ffh
mov 40h,#0ffh
mov 72h,#0ffh
mov 44h,#0ffh
mov 74h,#0ffh
mov 31h,#0ffh
mov 71h,#0ffh
mov 41h,#0ffh
mov 73h,#0ffh
mov 45h,#0ffh
mov 74h,#0ffh
lcall X0630
mov a,6eh
anl a,#7fh
orl a,#50h
mov 6eh,a
mov dptr,#X18ff
movx @dptr,a
X010c: lcall X0a0f
mov dph,#0bbh
mov a,#9bh
movx @dptr,a
lcall X0134
lcall X04e4
lcall X0907
ajmp X010c
;
X0120: mov dptr,#X1910
movx a,@dptr
jnz X0133
mov a,tl0
anl a,#7fh
orl a,#50h
movx @dptr,a
mov dptr,#X18ff
movx @dptr,a
mov 6eh,a
X0133: ret
;
X0134: jnb 2fh.6,X0142
djnz 39h,X0142
mov 39h,#0ah
jnb 2ah.6,X0142
cpl p2.3
X0142: ret
;
X0143: mov dph,#0bah
movx a,@dptr
jnb acc.6,X0150
jnb acc.7,X0150
ljmp X01b8
;
X0150: mov dph,#0b9h
movx a,@dptr
mov c,acc.0
orl c,acc.1
jnc X0170
mov c,acc.2
orl c,acc.3
jnc X0170
mov dph,#0b8h
movx a,@dptr
mov c,acc.0
orl c,acc.1
jnc X0170
mov c,acc.2
orl c,acc.3
jc X01b8
X0170: mov dph,#0bah
movx a,@dptr
jnb acc.7,X017a
jb acc.6,X01b8
X017a: mov 2dh,#0ffh
mov 2ch,#0ffh
mov 2bh,#0ffh
clr 29h.2
mov 6ah,#10h
mov 68h,#0ffh
mov 67h,#0ffh
mov 69h,#0ffh
mov 30h,#0ffh
mov 70h,#0ffh
mov 40h,#0ffh
mov 72h,#0ffh
mov 44h,#0ffh
mov 74h,#0ffh
mov 31h,#0ffh
mov 71h,#0ffh
mov 41h,#0ffh
mov 73h,#0ffh
mov 45h,#0ffh
mov 74h,#0ffh
ljmp X0206
;
X01b8: mov dph,#0b8h
movx a,@dptr
cjne a,2dh,X01c5
mov 67h,#80h
ljmp X01cc
;
X01c5: djnz 67h,X01cc
mov 2dh,a
acall X0120
X01cc: mov dph,#0b9h
movx a,@dptr
cjne a,2ch,X01d9
mov 68h,#80h
ljmp X01de
;
X01d9: djnz 68h,X01de
mov 2ch,a
X01de: mov dph,#0bah
movx a,@dptr
cjne a,2bh,X01eb
mov 69h,#0f0h
ljmp X01f0
;
X01eb: djnz 69h,X01f0
mov 2bh,a
X01f0: anl a,#3fh
mov b,a
mov a,2bh
anl a,#0c0h
orl a,b
mov 2bh,a
mov dptr,#X1802
mov a,2dh
movx @dptr,a
inc dptr
mov a,2ch
movx @dptr,a
X0206: jb 29h.0,X023e
jb 2bh.3,X0211
mov a,#10h
ljmp X023a
;
X0211: jb 2bh.2,X0219
mov a,#20h
ljmp X023a
;
X0219: jb 2bh.5,X0221
mov a,#30h
ljmp X023a
;
X0221: jb 2bh.0,X0229
mov a,#40h
ljmp X023a
;
X0229: jb 2bh.7,X0235
mov a,#0
cpl 29h.4
setb 29h.0
ljmp X023a
 

AlbertHall

Joined Jun 4, 2014
11,674
I am not familiar with the 8051 however I know that on other processors moving existing code around may fail if the code now crosses a page boundary where it didn't before and other similar effects.

You could put your new code in some part of memory not currently used and put a call to your code where you want it. The instruction(s) that were originally at the location of the new call location will need to be moved to the end of you new code. You will need to check that there are no references, calls, jumps. etc to the location of the new call instruction.
 

Thread Starter

furtsiv

Joined Mar 7, 2017
16
my dissasembled code does not have MOVC instruction wich i think is the only one that can be an issue if i move programe around , please anyone correct me if i'm wrong
calls like ACALL and LJMP goes to labels instead of addresses ,
any ideas ?
 

LesJones

Joined Jan 8, 2017
3,640
Lables are just sybolic addresses. All you need to do is to put something in front of the addres so it is no longer interpreted as an address by the assembler. For example change X0819 to LocX0819 I have used Loc to stand for location. When you go through the disassembly you will slowly work out what various parts of the code do. For example you may find a subroutine that produced a delay of one second you could change the label to" Del1sec" for example. At first I normaly leave the label contining the address as well as the one that means something to you. Once I have finished I assemble the unmodified code and verify that the addess in the list file from the assembly matches the original address. I normaly start off by identifying instructions that deal with I/O ports. You than know by looking at the schematic what that part of the code is doing.. For example if that I/O port is connected to an LCD display you know it is writing data to the display or getting some status information. (I don't know the 8051 so it could be that I/O ports look just the same as any other address on the memory map.)

Les
 

Thread Starter

furtsiv

Joined Mar 7, 2017
16
thanks everyone ,i found it ! without changing code offset at all
the main hex start with : LJMP 002CH
so i just changed that address to my personal code address (at the end of memory ) and when my code finish the job it jump to 002CH and everything goes fine
this is especially done to make the main hex run for limited time of restarts then stop ,like a trial version
 
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