Simple Project vs Structured Project

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Hi all,

What the difference between a Simple Project and a Structured Project?

You can use Ladder, ST and SFC in either project type on a Q Series, but only in a structured project can you use Structured Ladder / FBD.

In a structured project you can create functions.

Is there anything else?


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GX Works2 Version 1.577B

Series: QCPU (Q mode)

Project Type: Simple Project

Language: Ladder;


Use Label checked ST option appear.

Structured Project:

Use label os checked by default





structured Ladder/FBD


Not Specify.

this is what i have here.


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A Structured project is the best way to go, It allows you to create functions & blocks you can call multiple times & saves you programming the same code many times.

It actually still creates the equivalent of a single block of ladder, however by using the same instance of a function block it actually passes the values for input parameters to temporary memories (these are actually M & D registers in the higher limits (so don't use them as set in the compiler settings) jumps over the end instruction  runs the code, passes any output variables to temporary memories & jumps back to the main program where the output memory is updated.

For example

A function block with 2 input parameters & one output parameter in code goes:

Load D200 Transfer D4000 (temporary memory)

Load D201 transfer D4001

Call P2000  (pointer to function)

L D4002 T  D202 (move result to D202)

ju P400  (Pointer)

rest of code


FEnd  (End of ladder)


L D4000

L D4001


Transfer D 4002



So it's really like one block of code but as the FEND instruction is the end of what would be the ladder scan, function blocks are code in an area that is not normally scanned but can be jumped to & returned many times.

It allocates the temporary memory addresses and pointers at compile time .

Very useful if you have say many motors or valves with auto/manual & status information in a program, you write the function once then call it for as many you require but use the same instance name i.e. Motor_Control., if you use a different instance it creates a subroutine for every one & increases amount of memory used.




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Thanks guys.

When I write a Structured Project to an FX Series PLC and then 'Read from PLC', it's read as a Simple Project without labels, as you described Parky. Is there any way to read the project as a Structured Projects with labels?

When you read the project from a higher-end model PLC, the project is read as a structured project with labels - is that right? Does this apply to all Q Series, iQ-R and iQF?

Thanks again,

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im not sure about FX, but on Q series if you upload the symbols information to the PLC then you can download it all back without losing anything. the only issue is that it takes a lot of memory up in the CPU so isnt normally worth it :(

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