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How to Write a specif value on a specific address

Created by: AutoGen_8099262 at: 2/25/2021 11:08 AM (10 Replies)

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2/25/2021 11:08 AM	Rate (0)
AutoGen_8099262 Member Joined: 2/17/2021 Last visit: 10/13/2022 Posts: 4 Rating: (0)	Hello everybody, I'm a new in SCL scripts so i'm facing some small troubles,i want to create an FC Block how has to entries one is the the Address of the MW( for example the User will write 20 if he wants to write on MW20) and the second is the Value (IN1:=20,IN2:=40 this will write 40 in MW20) I'll appreciate your help.

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2/25/2021 11:42 AM	Rate (0)
T_Ebrahem Silver Member Joined: 1/2/2017 Last visit: 7/23/2024 Posts: 285 Rating: (24)	Hi one question, your addresses are already created as a tags? regards T_Ebrahem
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2/25/2021 11:53 AM	Rate (0)
AutoGen_8099262 Member Joined: 2/17/2021 Last visit: 10/13/2022 Posts: 4 Rating: (0)	No, But the thing is that all i'll need is tow entries for my block the number of the word MWxx and the value as described above.

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2/25/2021 12:43 PM	Rate (1)
T_Ebrahem Silver Member Joined: 1/2/2017 Last visit: 7/23/2024 Posts: 285 Rating: (24)	Yes but if the tag is not exist how you will write it? My suggestion is to create a DB with array of words, each value will have index. then your input is the index, which is the address in your case, and the value. DB.myArray[address] = value if you give more details of what you want to do with these then I can help you further.
	Disclaimer: While I strive to ensure that the content of posts and answers is accurate and complete, my posts and answers are provided “as is” and “as available.” Your use of my posts and answers content is entirely at your own risk.
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2/25/2021 12:45 PM	Rate (1)
qwazee Platinum Expert Joined: 3/30/2020 Last visit: 11/19/2024 Posts: 4968 Rating: (1012)	AutoGen_8099262 Hello everybody, I'm a new in SCL scripts so i'm facing some small troubles,i want to create an FC Block how has to entries one is the the Address of the MW( for example the User will write 20 if he wants to write on MW20) and the second is the Value (IN1:=20,IN2:=40 this will write 40 in MW20) I'll appreciate your help. Hello. Your question implies indirect addressing. It is not a topic for a beginner (of using SCL). Not stating which PLC hardware is used also presents a problem. Assuming you are using the S7-1200 or S7-1500.. Visit the in-software help to look up all the PEEK and POKE instructions. Select the one that is appropriate for your usage. (Keep in mind that %MW20 and %MW21 overlaps on %MB21.) ~
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2/25/2021 12:52 PM	Rate (0)
qwazee Platinum Expert Joined: 3/30/2020 Last visit: 11/19/2024 Posts: 4968 Rating: (1012)	T_Ebrahem Yes but if the tag is not exist how you will write it? My suggestion is to create a DB with array of words, each value will have index. then your input is the index, which is the address in your case, and the value. DB.myArray[address] = value if you give more details of what you want to do with these then I can help you further. Hello T_Ebrahem. It is good to receive a contribution from you aiming to help. Thank you. I share you confusion on why the Topic Starter would be wanting to write to M-bit memory. The use of DBs would make more sense. Moreso for making use of the power that arrays give. Let us for the moment assume that there is a good reason for the question. I would want to point out to you that it would be possible to write/read to M-bit memory even though there is no tag declared. The memory areas for input / output / M-bits are already there to use and does not need tags. Working without tags can however deliver some interesting coding bugs. It is in my view a poor design choice to work without tags or at least some indication that a memory area is occupied. Best health to you.
	Last edited by: qwazee at: 02/25/2021 12:53:28 Activities of this user is voluntary. There is no obligation or liability placed on this user. Though optional, your 'please' and 'thank you' is highly valued.
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2/25/2021 1:38 PM	Rate (1)
Towome Platinum Expert Joined: 7/9/2015 Last visit: 11/19/2024 Posts: 4028 Rating: (603)	Hi, please also have a look in the following FAQ: In STEP 7 (TIA Portal), how can you implement indirect addressing in an SCL program? Perhaps you work with AT command and you can construct an AN pointer. There is also a good FAQ which copys value frome source to destination. How can you construct an ANY pointer in S7-SCL using the AT function? Regards, Towome
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2/25/2021 4:15 PM	Rate (0)
AutoGen_8099262 Member Joined: 2/17/2021 Last visit: 10/13/2022 Posts: 4 Rating: (0)	thank you your answer was very helpful, i solved the problem i'll write the script below This script has 3 entries the address of Word, his length, and the value FUNCTION FC70 : VOID VAR_TEMP j : INT; C : INT; DIVi : INT ; // variables temporaires END_VAR VAR_INPUT i :INT; VA : WORD ; L_Byte : INT; END_VAR C:= i+L_Byte+1; FOR j := i TO C BY 2 DO MW[j] := VA; END_FOR ; ; END_FUNCTION

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This contribution was helpful to 1 thankful Users Towome

2/25/2021 4:34 PM	Rate (1)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 11/19/2024 Posts: 15406 Rating: (2446)	If there is ever a case for pushing back to fully understand a customer request before going off and making a horrible design decision that can wreak complete havoc on PLC programming. @qwazee stated it very wizely. While the SCL logic might do what you are asking for help on, I suspect in the future you will come back and ask the right way to solve the customer's real problem rather than allowing direct and random memory WRITE access. You can have a wonderfully running process and suddenly someone enters the wrong address and your block overwrites a mission-critical piece of data. Perhaps if you explain the reason someone thinks it is a good idea to make random writes to M-memory, we might be able to suggest a way to interpret the user input and perform a deterministic action. Like instead of actually writing to memory, write to DB that emulates M-memory space, and if the user requested memory change makes sense, apply it to the process. Otherwise, push a pop-up dialog or new screen on the HMI to indicate an invalid address / value combination was submitted. In essence, buffer the requests, and to be honest, completely avoid using M-memory on modern Siemens PLCs. Siemens recommends this as well. AutoGen_8099262 thank you your answer was very helpful, i solved the problem i'll write the script below This script has 3 entries the address of Word, his length, and the value FUNCTION FC70 : VOID VAR_TEMP j : INT; C : INT; DIVi : INT ; // variables temporaires END_VAR VAR_INPUT i :INT; VA : WORD ; L_Byte : INT; END_VAR C:= i+L_Byte+1; FOR j := i TO C BY 2 DO MW[j] := VA; END_FOR ; ; END_FUNCTION
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2/25/2021 4:43 PM	Rate (0)
AutoGen_8099262 Member Joined: 2/17/2021 Last visit: 10/13/2022 Posts: 4 Rating: (0)	i totally agree with you, like you've listed Accessing directly to a potential Process Variable Memory isn't that safe, but for real i'm just studying and understanding how SCL Scripts work, i'll check everything related to DBs Write/Read..Etc and thank you for your information. You'are very helpful guys

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