How can see where the value is changing?

DEAR FRITZ,

I HAVE A POINTER PROGRAM TO EXTRACT PIW/PQW ADREESS

TO WORD FORMAT.

THE PROGRAM(STANDARD FC) IS GIVEN BELOW:-

WHEN THE FC IS CALLED IT LOOKS LIKE

THE VALUE OF AR1 REMAINS SAME I.E DW#16#870000A8

HOW CAN I SEE ,WHERE THE VALUE IS CHANGING.

BUT THE VALUE OF MW40 IS CORRECT.

CAN YOU PLEASE EXPLAIN.THE REASON.

THANKS & REGARDS,

SAMIR

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Split from What's the mean , L D [AR1,P#2.0].

SAMIRKM

L     P##IN_Address               //INPUT

LAR1

L     1                                     

SLD   4

+AR1

L     D [AR1,P#0.0]             <-- starting from here, in ACCU 0 

SRD   3                           

T     #OUT_Address             //OUTPUT

DEAR JACEK D,

WHAT U HAVE MENTIONED ,I AM WELL AWARE OF 

THAT ,I WANT TO KNOW ,HOW THIS VALUE AR1(DW#16#870000A8)

IS GENERATED ,AND IT IS ALWAYS SAME.

IS IT POSSIBLE TO ACCESS INDIVIDUAL BYTE OF AR1.

THANKS & REGARDS,

SAMIR

SAMIRKM

DEAR JACEK D,

WHAT U HAVE MENTIONED ,I AM WELL AWARE OF 

THAT ,I WANT TO KNOW ,HOW THIS VALUE AR1(DW#16#870000A8)

L     P##IN_Address               //INPUT <-- here the address in the memory of IN_Address is read, IN_Address seems to be of POINTER datatype (reading online help on POINTER format can be helpful)

LAR1 <-- then it's loaded to AR1

L     1  <-- from here...

SLD   4

+AR1 <-- ... to here, the offset of 2 bytes is added to AR1 (3 completely useless lines BTW)

L     D [AR1,P#0.0] <-- so, here part of the POINTER starting at offset 2.0 is load to ACCU 0, in this part byte.bit address of variable assigned to IN_Address is stored

SRD   3 <-- this strips the bit address part off

T     #OUT_Address             //OUTPUT <-- and byte address only is output

WHEN THE FC IS CALLED IT LOOKS LIKE

CALL  "TEST"

IN_Address :=PIW4

TMP_Address:=MW40

 

SAMIRKM

IS IT POSSIBLE TO ACCESS INDIVIDUAL BYTE OF AR1.

TAR1 loads contents of AR1 to ACCU 0, then you can do anything to it.