fritz

Dear all

allow me say thatyou are both correct and it seems that there is a bit of a misunderstanding.

It is of course imperative to ensure that the correct DB is open before you do any indirect addressing of its elements (sohdhosseiniis correct concerning this as he also proved in his video, quite a nice effortI must say).

jacek dis however also correct as it is NOT required to open the correct DB's at the point of "presetting" the address registers(before the"LAR1 P#DBX 0.0" and "LAR2 P#DBX 0.0" commands).

As we are talking about not needed commands, allowme too to proposea runtime optimisation of the logicbased on the following changes:
- Usage of both DB registers and no need to open each DB in each loop(Note: preferably done in an FC, be mindful when doing so in an FB as the DB2 register is used for the IDB).
- Usage of only AR1 (the "P#x.y" offset will be used if the start addresses differ)
Note: I kept the BYTE wise comparison, aWORD or DWORD based comparisonwould of course be even better (less loops to do):

LAR1 P#0.0// Load start address into AR1 OPNDB 1// open first DB via DB register 1 OPN DI 2// open second DB via DB register 2 L 64 LOOP: T #_Loop_counter // Loop counter (TEMP variable type INT) L DBB [AR1,P#0.0] // use "P#x.y" offset if DB1's start address is higher than DB2's L DIB [AR1,P#0.0] // use "P#x.y" offset if DB2's start address is higher than DB1's <>I JC CONT// leave loop if difference encountered (or do other handling here) +AR1 P#1.0// bump AR1 by 1 Byte L #_Loop_counter LOOP LOOP JU END CONT: NOP 0// do whatever needs to be done here if difference encountered END: NOP 0
I hope this helps

naqqash

Thank you very much for the reply. I have now three options but not sure which one to decide so now i think it would be better to describe my whole task. The three options are 1) using STL the code you suggested. Having error on command 'opn db 200' don't know why (2) Use the function which you have suggested (3) the thing I was trying myself in which I am comparing a specific element of the DB with some number. I did not know how to write DB element individually at the input of comparator so what i did is that I have first moved it into memory and then used that memory to compare. Worked!

The overall task description is this,

I have 2 PLCs 414 and 417-4H .. I am trying to make communication between both PLCs using ethernet. On hardware side it is working fine, thanks to tutorial on siemens website. Second to make them communicate together on the software side I am using PUT and GET command. Found one example on the website that was really helpful.

Now my main PLC is 414 in which DB200 is and the other is 417 in which DB201 is. What I am thinking is that when the 417 finish some task it change some value in DB201 and as in my 414 PLC I am using GET command to get data to DB200 so when the data come to this DB upon comparison the way I have said earlier do some task by this PLC. It is kind of a DCS system but I am trying to make it by myself instead using some already existing solution. Trying to learn.

BTW I am so far successful untill data exchange between two PLCs using GET.

and YES your right about 'naqqash'.. Actually the art is known as 'naqqashi' and the one who does it is naqqash.