would you give me counter example?

minhyuk

Member
Join Date
Feb 2008
Location
Korean
Posts
12
Hi all, Again!
I heard that address conflict is very difficult to find in Ladder Diagram!!

I didn't seen before!!

Would you give me a Counter Example?
 
minhyuk said:
Hi all, Again!
I heard that address conflict is very difficult to find in Ladder Diagram!!

I didn't seen before!!

Would you give me a Counter Example?
Anybody reply this article!! PLZ...
 
Hi Mickey!
I am a developer for provide better edit tools.
so, can you explain to me, using Standard Ladder Diagram?
 
minhyuk said:
Hi Mickey!
I am a developer for provide better edit tools.
so, can you explain to me, using Standard Ladder Diagram?

Two examples:

http://www.plcs.net/chapters/count15.htm

Below is an Allen Bradley ( SLC) example.

Counter_1.jpg
 
no no...mickey!
I need a Count Example for Address Conflict!
Address Conflict is critical Error!! you know?

Sorry About My English~
Regards.
 
minhyuk said:
no no...mickey!
I need a Count Example for Address Conflict!
Address Conflict is critical Error!! you know?

Sorry About My English~
Regards.

Sorry, my bad. I misunderstood your question. And sence I don't
understand exactly what you are asking for I don't have an ansewer. Hopefully someone else will check in with an ansewer.
 
In systems with an addressable memory space it is important that there not be multiple instructions in a program which affect the same memory space in a conflicting manner.

Many programming packages can show the usage of memory spaces which are the source or target of instructions providing an aid to selecting a non-used memory space for other instructions.

Many times these 'usage' views cannot show as 'used' memory space which are the source or objects of instructions which deal with multiple memory spaces in one instruction. The target memory locations of an instruction which moves a block of values from one memory space to another may not be not be fully accounted when the 'usage' map is created.

Also programming packages may not be able to warn if a particular memory location is used by multiple instructions in incompatible ways. For example - one instruction may treat a memory location as an double size integer while another may treat it as a floating point value. These incompatibilities may also be interpreted as 'address conflicts'.

It is not a weakness of Ladder Diagram programming which would allow or mask these address conflicts. It is a weakness of an underlying interpreter/compiler whicch allows this. Any of the programming languages (particularly in PLCs) are suseptible to this weakness.

Better interpretation of block type instructions may help in 'usage' views. Though block instructions whose source/target/block size varies at runtime are basically impossible to take into account in 'usage' views'.

The emergence of 'strong typing' in programming packages may help in the second example of 'address conflicts'.
 
Hi Bernie Carlton!
Many Programming Language Compilers had Strongly Typing Mechanism, so Any Program that compiled by Strongly Compiler, it is safe program without type error. but, these programming languages has many types, so must required type checking.

this Strongly typing compiler find out type error in static time.(when compiling..)

in Ladder Diagram, there are only one type(boolean: XIO, EN, DN, OTE)
except function block or function.

strongly typing in Ladder Diagram is really need?

Regard.
------------------------
Minhyuk, Kwon
http://pllab.kut.ac.kr/~batman
Programming languages Laboratory
Korea Technology and Education University
 
The bit types you are referring to are only one aspect of Ladder Diagram programming. Data is routinely handled in words and double word formats, possibly as floating point numbers. Words may also be used to form shift registers and sequencers. These uses of the device memory space may be compromised in the manners I mentioned.

Many implementations allow accessing of what would normally be used as word memory as individual bits. The opposite is also true. Some allow accesing of groups of bits in a word type manner. All these uses contribute to possible address conflicts which may be difficult to find quickly.

In most cases only rigorous documentation by the programmer can aid in preventing these problems.
 

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