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Dynamic (Variable) Any Pointer

Created by: TEBANCH at: 5/24/2012 5:51 PM (9 Replies)

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5/24/2012 5:51 PM	Rate (0)
TEBANCH Silver Member Joined: 3/25/2008 Last visit: 1/28/2022 Posts: 232 Rating: (20)	Hello dear colleagues. After a long time working with other PLC/Automation Brands i'm back to the Siemens PLC World. I havea ilttle problem trying to create a "dynamic pointer"; let me explain a little bit more: I have to send 200 bytes of data from my PLC to a"measuring" device over profinet, i have created an FB to handle the data exchange between PLC and "measuring" device. My FB has an input parameter "IOAddres"and i use itto knowwhich is the IO addres that the device is using; so using this input parameter i wan to to create a dynamic pointer to send data to my"measuring" device using SFC20 in several instances for example lets we suppose IOAddes is equal to 100, then the FB will map data starting at QB100 and finishing on QB199, but i have to fragmentthis large packetof data into small packets which lenght is diferent each other for example Packet 1 will be QB100 to QB109 (ten bytes), Packet2 will be QB110 to QB115 (sixteen bytes), Packet3 will be QB116 to QB119 (four bytes)... and so on. So far i have solved this task using following code: L B#16#10S7 pointers constant10 Hex T LB 0First byte ofIndexvariable (any pointer) (Temp Var) L B#16#2Data type to be used (Byte) T LB 1Second byte ofIndex variable (any pointer)(Temp Var) LLenghtLenghof data to be transfered (Temp Var) T LW 2Third and Fourth Byte ofIndexvariable (any pointer)(Temp Var) L 0Set to 0 since we are not handlig a DB??? T LW 4Fifth and sixth ofIndexvariable (any pointer)(Temp Var) LIOAddresFB Input Parameter LOffsetVariable to add an offset to IOAddres value, this is de dynamic part +I T #dUMMY Temp var to holdthe sum result L P#Q 0.0 Load Start addres for outputs LAR2 I used AR2 but what ifi use AR1? L #dUMMY SLD 33 bit left Rotation of IOAddres+Offset +D Sum AR2+(3 bit left Rotation of IOAddres+Offset) L DW#16#FFFFFFF8 Mask 3 less significant Bits, ADI do not know why , the result is the same than in theprevius sum LAR2AR1 can be used as well? T LD 6last 4 bytes ofIndexvariable (any pointer) CALL "BLKMOV" SRCBLK :=#StationID Array 10 bytes long RET_VAL:=#dUMMY DSTBLK :=#INDEX My dynamic pointer My big questionsare: 1.is there a waytomake thisina simpler way? 2. Do you have anysuggestion in order to make this code better? 3. Do you see mistakes or possible failures in the code? (it works, but i have no tested 100%). Anysuggestion will be very wellcome and appreciate, thanks all you for your help andhave a very good day. Best Regards.
	Keep working!
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5/24/2012 7:44 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	Hard to undarstand your intention. Have you (shure you have) looked at SFC for transfering over profinet DPRD_DAT and DPWR_DAT, what is wrong with them?

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5/24/2012 9:34 PM	Rate (5)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 11/19/2024 Posts: 3027 Rating: (1057)	Hello TEBANCH here are a few suggestions from my side: 1.) You don't need to use AR2 (nor AR1), it is actually doing nothing in your code as your ANY Pointer is constructed in the TEMP area. 2.) The "L DW#16#FFFFFFF8" followed by"AD" is also superflous. It's aim would be to ensure that the bit address of the Pointer is zero, but it will be anyhow due to the SLD3. 3.) If this is indeed an FB and should you need to use ARx somewhere in it, prefferably stay away from AR2 (it is used as the Multi Instance offset in an FB, see also HERE for more on this). 4.) Onepossibly optimised version of your logic couldlook like below (Note: I have not tested it, pelase do so): [code]L W#16#1002 // S7 pointer constant 10hex; Data type 02hex (= Byte) T LW 0 // --> Byte 0 & 1 of ANY Pointer L #Length // Lengh of data to be transfered in BYTES (calculated elsewhere) T LW 2 // --> Byte2 &3 of ANY Pointer L 0// Set DB number to 0 (not applicable as Q are is used) T LW 4 // --> Byte4 &5 of ANY Pointer L #IOAddress// Q Base address L #Offset //Q Byte offset (dynamic part) +I // add together =Q start Byte number SLD 3 // convert to S7 Pointer L DW#16#82000000// Load Q Area ID (82hex) OD // add toQ address T LD 6 // --> Byte6 -9 of ANY Pointer CALL "BLKMOV" SRCBLK :=#StationID RET_VAL:=#dummy DSTBLK :=#INDEX // ANYPointer in LB 0-9[/code] That's all I can think of and I hope ithelps
	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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This contribution was helpful to 8 thankful Users dchartier smiffy TEBANCH Ste39 Ikkez Vincent YuHang Millsite Marino

5/25/2012 5:50 PM	Rate (1)
TEBANCH Silver Member Joined: 3/25/2008 Last visit: 1/28/2022 Posts: 232 Rating: (20)	Hello thanks a lot for your answers. Marko Bursic Hard to undarstand your intention. Have you (shure you have) looked at SFC for transfering over profinet DPRD_DAT and DPWR_DAT, what is wrong with them? I have not look at them but my problem is not how to send data over profinet, my problem was how to build/assembly a pointer with variable length and variable byte addres (I'm sorry if i did not provided a good description of the problem), i'm attaching "FB_2",source file that's where i'm using the "variable pointer" technique,any way i also will take a look to those blocks (DPRD_DAT and DPWR_DAT), thank you. Dear fritz, the code you provided is excellent , now i have learnedalot thanks to you. Every one, havea really good weekend. Attachment FB2_V0_2.zip (829 Downloads)
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This contribution was helpful to 1 thankful Users fritz

10/22/2014 4:14 PM	Rate (0)
abdurrahim Posts: 6 Rating: (0)	Dear Experts, This sample program works perfectly byte-wise.(move from source to destination byte by byte dynamically) I would like to perform the same task bit-wise. (move from source to destination bit by bitdynamically) For example, I will transfer 5 bits from DB1.DBX 3.4 to DB2.DBX 6.0 for the first cycle. In thenext cycle, I will transfer 11 bits from DB1.DBX 2.0 to DB2.DBX 3.0. I will indicate the indexbit for the source anddestination seperately. And plus, length will be also provided ( How many bits that I will transfer). It may sound like a little bit silly task to do in PLC but I really need it because I will implement a light curtain in our plantwhichperform a hole detection on the steel strip. The device will transmit the raw data by Profibusin terms of bit streaming. In other words, the device has 368light beam on it and the state of each beam can be reached byProfibus. I hope the implementation is clear for you and look forward to hearing from you soon. Thanks in advance & Kind regards
abdurrahim Posts: 6 Rating: (0)
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10/22/2014 6:00 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 10/21/2024 Posts: 1547 Rating: (537)	Well you cannot use BLKMOV for anything other than byte aligned data transfer (that is address and data legth are both exactly divisible by 8). So you will need to use a read-modify-write method:- 1) Read the entire source byte that contains the bits you want to transfer into a temporary byte 1. 2) Bit-wise AND the temporary byte 1 to mask off only the bits you are intersted in. 3) Bit shift the temporary byte 1 so that the bits line up with the bit position required in the destination byte. 4) Read the entire destination byte where you want to write the data into another temporary byte 2. 5) Mask out the bits in the temporary byte 2 (making them all 0's) then bit-wise OR temporary byte 2 with temporary byte 1 to "mask in" the new bits over the old bits. 6) Write the resultant value from 5) back to the destination byte. If you only want to write the source bits into the same bit positions of the destination area, then you can skip step 3). Here is my first stab at some psuedo code to do it. This has obviously not been tested, but it looks like it may have a chance. If you intends to put the data in the same bit position as the source then you can leave out the DstBitStart, BitShift inputs and the shift code. Inputs SrcBitStart : INT // Start bit for source byte address (0-7) DstBitStart : INT // Start bit for destination byte address (0-7) BitLength : INT // Amount of bits to be copied Temps Tmp1 : BYTE // Temp store for source data Tmp2 : BYTE // Temp store for dest data SrcMask : BYTE // Mask value for masking off unused bits DstMask : BYTE // Mask value for masking off unused bits BitShift : INT // Bitshifts required 0=none >0 = left <0=right Code SrcMask := (((2 ^ BitLength) - 1) << SrcBitStart) // ^=power, <<=left shift n bits DstMask := NOT(((2 ^ BitLength) - 1) << DstBitStart) // ^=power, <<=left shift n bits NOT=bitwise NOT Tmp1 := SourceByte AND SrcMask // Read source byte and mask off the only bits we are interested in BitShift := DstBitStart - SrcBitStart // Calculate which way and how far to shift data bits IF BitShift > 0 THEN // Need to shift left as dest start is further left that source start Tmp1 := Tmp1 << BitShift // Shift left the requisite number of bits <<=shift left n bits IF BitShift < 0 THEN // Need to shift right as dest start is further right that source start Tmp1 := Tmp1 >> BitShift // Shift right the requisite number of bits >>=shift right n bits Tmp2 := DestByte // Read dest byte Tmp2 := Tmp2 AND DstMask // Mask out the bits in the destination word Tmp2 := Tmp2 OR Tmp1 // Mask in the source data to the destination data DestByte := Tmp2; // Write back the modified destination data
	Last edited by: smiffy at: 10/23/2014 10:31 AM Last edited by: smiffy at: 10/22/2014 6:15 PM Fix coding error in mask calculation Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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10/22/2014 6:50 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 10/21/2024 Posts: 1547 Rating: (537)	I was bored, and like a challenge, so I thought I try out my code. My prefered coding language is SCL. The code I came up with is shown below and a quick test shows that it works. It might be a bit more that you require, as it also handles bit shifting to allow you to put the bits in a different position in the destination byte to where they were in the source byte. Obviously, my code is just using single bytes that are supplied, but I'm sure you could adapt it to your needs. You would just have to add a bit of logic to work out what byte your bit address falls in and input it to the SrcByte input and calculate the SrcBitStart and DstBitStart values. I hope it gives you some ideas . [code] FUNCTION_BLOCK FB100 VAR_INPUT SrcBitStart : INT; DstBitStart : INT; BitLength : INT; SrcByte : BYTE; END_VAR VAR_OUTPUT MyReal : REAL; DstByte : BYTE; END_VAR VAR Tmp1 : BYTE; Tmp2 : BYTE; Mask : BYTE; BitShift : INT; MaskTmp : INT; END_VAR IF BitLength > 0 THEN MaskTmp := REAL_TO_INT(2 ** INT_TO_REAL(8)) - 1; Mask := SHL(IN:=INT_TO_BYTE(MaskTmp),N:=SrcBitStart); Tmp1 := SrcByte AND Mask; BitShift := DstBitStart - SrcBitStart; IF BitShift > 0 THEN Tmp1 := SHL(IN:=Tmp1,N:=BitShift); END_IF; IF BitShift < 0 THEN BitShift := ABS(BitShift); Tmp1 := SHR(IN:=Tmp1,N:=BitShift); END_IF; Tmp2 := DstByte; Tmp2 := Tmp2 OR Tmp1; DstByte := Tmp2; END_IF; END_FUNCTION_BLOCK [/code]
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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10/23/2014 10:29 AM	Rate (0)
abdurrahim Posts: 6 Rating: (0)	Dear smiffy, I tested the program on a CPU today but it did not perform propely as you can see in theattached photo. Source bits are all FALSE but destination bits are remaining all TRUE. Could you please have a look at your programif you would not mind. Thanks for your great effort Attachment FB100_Simatic_Manager_Test.jpg (778 Downloads)
abdurrahim Posts: 6 Rating: (0)
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10/23/2014 11:17 AM	Rate (1)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 10/21/2024 Posts: 1547 Rating: (537)	Yeah, I realised that I had made a boo-boo last night after I had left work and was at the gym . Now that is a sign of an obsessed programmer. He thinks about his code whilst at the gym and can debug it in his head. I need more hobbies . I have altered my pseudo code post and I have altered my SCL code now too. Just using a simple OR means that the destination bits will incorrectly "win" in battle when they are 1's and the source bit is a 0. So what you need to do is ensure that the destination bits to be written are always 0. That way the source bits will decide what the destination bits will be. Here is the new code:- [code] FUNCTION_BLOCK FB100 VAR_INPUT SrcBitStart : INT; DstBitStart : INT; BitLength : INT; SrcByte : BYTE; END_VAR VAR_OUTPUT DstByte : BYTE; END_VAR VAR Tmp1 : BYTE; Tmp2 : BYTE; SrcMask : BYTE; DstMask : BYTE; BitShift : INT; MaskTmp : INT; END_VAR IF BitLength > 0 THEN MaskTmp := REAL_TO_INT(2 ** INT_TO_REAL(BitLength)) - 1; SrcMask := SHL(IN:=INT_TO_BYTE(MaskTmp),N:=SrcBitStart); DstMask := NOT SHL(IN:=INT_TO_BYTE(MaskTmp),N:=DstBitStart); Tmp1 := SrcByte AND SrcMask; BitShift := DstBitStart - SrcBitStart; IF BitShift > 0 THEN Tmp1 := SHL(IN:=Tmp1,N:=BitShift); END_IF; IF BitShift < 0 THEN BitShift := ABS(BitShift); Tmp1 := SHR(IN:=Tmp1,N:=BitShift); END_IF; Tmp2 := DstByte; Tmp2 := DstByte AND DstMask; Tmp2 := Tmp2 OR Tmp1; DstByte := Tmp2; END_IF; END_FUNCTION_BLOCK [/code]
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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This contribution was helpful to 2 thankful Users MicroMan abdurrahim

10/23/2014 1:54 PM	Rate (0)
abdurrahim Posts: 6 Rating: (0)	Dear smiffy, The modified program works perfectly. I appreciate your help & support. I have to say that the world needs such obsessed programmers like you. keep it up mate Thanks & Kind regards
abdurrahim Posts: 6 Rating: (0)
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This contribution was helpful to 2 thankful Users smiffy MicroMan

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