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Pointers Doubt

Created by: ssmanku1699 at: 10/19/2011 9:19 AM (9 Replies)

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10/19/2011 9:19 AM	Rate (0)
ssmanku1699 Experienced Member Joined: 8/10/2009 Last visit: 9/12/2023 Posts: 166 Rating: (2)	Dear User's , Can anyone please explain me the meaning for the under written code in STL ? I will be thankful to him. L P##DVC_StrtAddr LAR1 L W [AR1,P#0.0] T #DB_No OPN DB [#DB_No] L D [AR1,P#2.0] LAR1 L DBD [AR1,P#0.0] T LD 0 // Control & Status area L DBW [AR1,P#4.0] T LW Thanks. Your's Truly, Sarabjot Singh Manku

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10/19/2011 9:50 AM	Rate (1)
MM1234 Posts: 270 Rating: (52)	Hello ssmanku1699, this is the help about the code I can give you: 1) L P##DVC_StrtAddr - here you load pointer to the starting address of your stuff 2) LAR1 - this commands transfers the pointer to address register 1, so you can use it for addressing and load other stuff freely etc. 3) L W [AR1,P#0.0] - here you load word from the specified address which is being pointed by address register 1, which isoffsset by 0 bytes and0 bits(that p#0.0,which seemssilly here, but it comes in very handy in loops etd.) 4) T #DB_No - you store the loaded value into variable DB_No, whichidentifies data block you use 5)OPN DB [#DB_No] -now you open the specified datablock 6) L D [AR1,P#2.0] - sameway as before, you load from address register, but now you load double word and you offset the data by 2 bytes (so i.e. if the original address wasi.e. MD20, now you are loading from MD22 (which wouldn't make sense, but you loaded word before, so it'sallright:-]) 7) LAR1 - same as before 8)L DBD [AR1,P#0.0]- now you are loading double wordfrom the address specified inyour new value from addressregister, however you load this double fromyouropened datablock, with no offset 9) T LD 0// Control & Status area- here you store the loaded value into double in the local memory at address0, this one I am not completely sure about though, you simply store it somewhere, you might find more informationregardingit in this topic- /tf/WW/en/Posts/39915,foremost the first reply from fritz(2nd post) 10) L DBW [AR1,P#4.0] -another load from your datablock, this time word which is offset by4 bytes(size of that double word from before) 11)T LW - here I feel like there's missing the number of the address in the local stack as it is in instruction 9 Hope this helps, if I'm wrong regarding the local stack thingie, someone will surely add the missing cents on that :)
MM1234 Posts: 270 Rating: (52)
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10/19/2011 10:33 AM	Rate (0)
ssmanku1699 Experienced Member Joined: 8/10/2009 Last visit: 9/12/2023 Posts: 166 Rating: (2)	Dear MM1234 , Thanks for your quick reply ! In my Program :- P##DVC_StrtAddr = P#db20.dbx6.0 If It is so then , Can you plz brief the output as per each network ? Code was:- L P##DVC_StrtAddr LAR1 L W [AR1,P#0.0] T #DB_No OPN DB [#DB_No] L D [AR1,P#2.0] LAR1 L DBD [AR1,P#0.0] T LD 0 // Control & Status area L DBW [AR1,P#4.0] T LW 4 Thanks. Your's Truly, Sarabjot Singh Manku

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10/19/2011 10:57 AM	Rate (0)
MM1234 Posts: 270 Rating: (52)	Hello ssmanku1699, I am afraid I am not sure what do you mean with the output of networks. Anyway, what I can tell you is following: If the pointer you provide is DB20.DBX6.0 without any other specification, then the data type is POINTER, which has 48 bits, first two bytes contain the number of DB and the other 4 points is exceeding (idk if the word is right) pointer, that specifies the starting address. So, what you do is load that whole POINTER data type and save that into address register. Then you load word from that address register with zero offset, so what you tell the machine is to load the first two bytes of the POINTER, which as I said before contain the number of your data block. Then you save that number (20 in your case) into variable DB_No and right after that open that desired data block 20. After that you load double word from the address register (which is same as before) with offset 2 bytes. That means that you load the whole exceeding pointer to the starting address of your data and save it to the address register, which in your case ise the DBX6.0. What this does is, that in the next instruction, when you use L DBD [AR1,P#0.0], the double word you are loading from your opened block (DB20) with no offset is taken from starting address in AR1, which is 6. So you are loading bytes 6-9 from datablock 20. Any further I can't go because this really depends on what you have saved in your datablock. Hope this helps, don't hesitate with any more questions.
MM1234 Posts: 270 Rating: (52)	Last edited by: MM1234 at: 10/19/2011 11:36 AM typos
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10/19/2011 12:39 PM	Rate (1)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 9/22/2023 Posts: 2987 Rating: (1033)	Hello ssmanku1699 here's my take on things onwhat your logic produces(assuming P##DVC_StrtAddr = P#db20.dbx6.0) L P##DVC_StrtAddr// load a value that points to start of the pointerinto accu 1 LAR1 // AR1 now points to the start address of the Pointer value (located in L memory of calling block, aka V memory) L W [AR1,P#0.0] // Load Pointers DB number fromV memory into accu 1 T #DB_No // Store DB number in variable OPN DB [#DB_No] // Open DB 20 L D [AR1,P#2.0] // Load Pointers address partfromV memory into accu 1 LAR1 // AR1 now contains the address part of the pointer (i.e.DBX6.0) L DBD [AR1,P#0.0] // Load DB20.DBD6 T LD 0 // Store in local memory L DBW [AR1,P#4.0] // Load DB20.DBW10 T LW 4 //Store in local memory I hope this helps
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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12/17/2011 11:52 AM	Rate (0)
trendsetter2k20 Posts: 9 Rating: (1)	Could Any One Explain the Differences of Using SLD 2 SLD 3 SLD 4 SRD 2 SRD 3 SRD 4 On which Situation Which Instruction should we use.
trendsetter2k20 Posts: 9 Rating: (1)
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12/17/2011 11:56 AM	Rate (0)
trendsetter2k20 Posts: 9 Rating: (1)	How to build a logic with Incremental Pointer of Varying Length DB1 Word 1 Should be Copied to DB2 Word-1 DB1 Word 2 Should be Copied to DB2 Word-2 DB1 Word 3 Should be Copied to DB2 Word-3 DB1 Word 4 Should be Copied to DB2 Word-4 DB1 Word 5 Should be Copied to DB2 Word-5 DB1 Word 6 Should be Copied to DB2 Word-6 DB1 Word 7 Should be Copied to DB2 Word-7 So on like that upto 100 Word on every 8 hrs.
trendsetter2k20 Posts: 9 Rating: (1)
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12/17/2011 12:10 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (149)	If you are thinking about the pointers then SLD3 is the right choice. let me explain also when it comes in use: If you to convert an address to pointer, for example read data stored at address MW100: 1. L P#M100.0// load a pointer with address m100.0 LAR1 // store in register ar1 L W[AR1,P#0.0] // load from address stored in AR1 with offset 0.0 (L MW100) 2. L P#100.0 //load a pointer with address m100.0 (it doesnt have defined area type) LAR1 L MW[AR1,P#0.0] // now we add area type M to pointer 3. L L#100 // load an dinteger of 100 SLD 3 // shift left 3 T AddrTemp //store like address temp L MW[AddrTemp] //load from MW area at adress 100 Look in defintion of pointer and you will find that first 3 bits are reserve for bit address like x.0 to x.7 so thats way you need to shift, pointer also has area type which could be added later (L MW[], we added M area) 4. L P#M100.0 // pointer=M100.0 T AddrTemp //store pointer L PIW[AddrTemp] // acces PIW100, area type is PI and last command changed are type from M area to PI area
	Last edited by: Marko Bursic at: 12/17/2011 12:16 PM
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12/17/2011 12:51 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (149)	trendsetter2k20 How to build a logic with Incremental Pointer of Varying Length DB1 Word 1 Should be Copied to DB2 Word-1 DB1 Word 2 Should be Copied to DB2 Word-2 DB1 Word 3 Should be Copied to DB2 Word-3 DB1 Word 4 Should be Copied to DB2 Word-4 DB1 Word 5 Should be Copied to DB2 Word-5 DB1 Word 6 Should be Copied to DB2 Word-6 DB1 Word 7 Should be Copied to DB2 Word-7 So on like that upto 100 Word on every 8 hrs. you can use BLKMOV (SFC20) with ANY pointers: source ptr: P#DB1.DBX0.0 WORD 100 destination ptr: P#DB2.DBX0.0 WORD100 It is assumed that begining of source and destination wordare onaddress 0.0 in datablocks, if not adjust statement DBX0.0 to match your block (Like DBX4.0 if the beginning is at 4.0)

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12/21/2011 8:08 AM	Rate (0)
trendsetter2k20 Posts: 9 Rating: (1)	Thanks Marko bursic I completed the Logic by myself i got hands of experiance in Both Memory Indirect Addressing & Register Indirect addressing I introduced the Loop concept into them so it's working fine. This is How i Did L #Source_DB_Number T #Source_DB_No L #Destination_DB_Number T #Destination_DB_No L #Source_Word_Start_Addres // Load Source Data Address as INT ex 0 or 2 or 4 ITD // Convert Source Addr as INT to DINT SLD 3 // Convert Source Addr as Pointer T #Sourc_Addr_Start // Trasnfer to a Local Area for Incrementing it During Loop LAR1 // Load AR-1 With the Source Data Word Starting Address L #Destinat_Word_Start_Addr // Load Destination Data Start Address as INT ex 0 or 2 or 4 ITD // Convert Destination Addr as INT to DINT SLD 3 // Convert Destination Addr as Pointer T #Dest_Addr_Start // Trasnfer to a Local Area for Incrementing it During Loop LAR2 // Load AR-2 With the Destination Data Word Starting Address L P#0.0 T #Point_1 L #Data_Length Jump: T #Loop_Count L #Sourc_Addr_Start L #Point_1 +D T #Sourc_Addr LAR1 #Sourc_Addr L #Dest_Addr_Start L #Point_1 +D T #Dest_Addr LAR2 #Dest_Addr OPN DB [#Source_DB_No] L DBW [AR1,P#0.0] OPN DB [#Destination_DB_No] T DBW [AR2,P#0.0] L #Point_1 L P#2.0 // Increment the Pointer by 16 bit for Handling Word Data +D T #Point_1 L #Loop_Count LOOP Jump NOP 0
trendsetter2k20 Posts: 9 Rating: (1)
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