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UDT vs DB

Created by: amrmabrouk at: 6/21/2010 3:42 AM (9 Replies)

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6/21/2010 3:42 AM	Rate (0)
amrmabrouk Posts: 13 Rating: (0)	Dear all can anyone tell me when to use UDT and when to use DB, and what is the ddifference betwwen them? Thanks in advance
amrmabrouk Posts: 13 Rating: (0)
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6/21/2010 5:18 AM	Rate (0)
IBN-Service Posts: 8946 Rating: (1000)	amrmabrouk Dear all can anyone tell me when to use UDT and when to use DB, and what is the ddifference betwwen them? Thanks in advance The UDT (=User Defined Datatype)is a datatype, means: a shape or token. You can use an UDT in different DB's. The DB (=DataBlock)itselve is the container of data. The UDT will not be loaded into the PLC but the DB.
IBN-Service Posts: 8946 Rating: (1000)
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This contribution was helpful to 5 thankful Users amrmabrouk Saruca abdulhadi1987 ArifinSabuz Peace man

6/21/2010 5:46 AM	Rate (0)
Berg Silver Member Joined: 1/17/2006 Last visit: 7/14/2025 Posts: 554 Rating: (29)	amrmabrouk Dear all can anyone tell me when to use UDT and when to use DB, and what is the ddifference betwwen them? Thanks in advance Hello, You can find informations about UDT and DB in chapters 4/9/11of the Programming with STEP 7 manual. Best regards.

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This contribution was helpful to 4 thankful Users how come Saravana kumar amrmabrouk ArifinSabuz

6/22/2010 3:09 PM	Rate (1)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi Amrmabrouk. Yes what IBM services and others have said is true. If you have bulk of data that you want to use again and again then it will be good practise to use UDT for all the data that are commonly required by all other blocks. For an eg : I have 3 motor block, then the common control are say run feedback, trip, EMPBS, local remote etc... then it would be easy to use UDT where i have entered all the data as said above and use it where ever i like and as many as times i like. Note : once you have created a UDT, and used it in the program, then changing any of the parameter or its type will cause a conflict then you have to update the block call in each usage... have fun....
	Jazz
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This contribution was helpful to 4 thankful Users amrmabrouk Saruca VR12 abdulhadi1987

5/20/2011 3:46 PM	Rate (0)
blowouter Posts: 32 Rating: (2)	hello all is the values in the udt constant once values declared cannot be changed if not how i can change it and where
blowouter Posts: 32 Rating: (2)
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5/20/2011 4:07 PM	Rate (1)
IBN-Service Posts: 8946 Rating: (1000)	you can change the values inside the UDT with editor anytime. But after, you must update your depending DB.
IBN-Service Posts: 8946 Rating: (1000)
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5/21/2011 10:09 AM	Rate (1)
gre_m Posts: 947 Rating: (45)	UDT is template created based on the basic data types. This is analogous to a custom data type, description of structures in other programming languages. That is a description of the data as INT, WORD. This is just a tool to simplify a complex data structure. DB - This is a reserved location in memory for data storage. DB elements are addressed, while elements of UDT are offset (field) from the beginning of the structure is reserved by UDT. Often to simplify working with DB, its content is described as a UDT. This allows you to write more comprehensible code of the program, it is easy to modify many of the same DB, if they described a UDT - enough to change the UDT
gre_m Posts: 947 Rating: (45)
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5/22/2011 12:18 AM	Rate (1)
Krish Silver Member Joined: 5/24/2007 Last visit: 4/24/2024 Posts: 284 Rating: (27)	Hi Generally UDTs are very helpful when you are using Object Oriented programming and it is veryhelp and simplifyyour programming workflow. Also when you would want to make standardsand definitions they are fine.But then UDT comes with a compromise they tend to increase the cycle time if used extensively. Accessing individual elements of the UDT in FC and FBs a lot of CPU is involved in handling them through registers. Problem is that all these are not obvious and also no information is available. But it is possible to test this directly in a program. The following document should show how it affects.(I downloaded it from the forum some long time ago.. I tried theentry on the document directly... but it no longer exists). Krish Attachment Memory requirements for word load command.pdf (1094 Downloads)

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This contribution was helpful to 1 thankful Users Saruca

5/23/2011 8:34 AM	Rate (1)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi all it is true that UDT takes a lot of space but it is very help full when you have to repeat same data again and again in various FB's Then again it depends on the programer to programer.... Have fun....
	Jazz
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This contribution was helpful to 1 thankful Users vainatey

11/24/2016 1:32 PM	Rate (1)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4760 Rating: (122)	New question published by AlfredoSA is split to a separate thread with the subject UDT1002. Best regards Min_Moderator

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This contribution was helpful to 1 thankful Users ArifinSabuz

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