s7 5.5 protected blocks

dwoodlock

Lifetime Supporting Member
Join Date
Nov 2012
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Cincy/nKY
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548
Working to add some logic to a press that we received from our HQ, and it has brand new controls (NICE!). Anyway an encoder is used so you get a positional readout from the main shaft.

Writing logic for a pressure test station in the die set, as I have done before and trying to use the cam evaluation blocks, for the sake of sticking to the original program structure and using what's already available. Unfortunately after tracing the HMI data addresses back to the PLC, I cant find them in use anywhere...

If the addresses are used in a protected block, will it keep them from showing on a x-ref????
 
From memory, the addresses used inside a protected block would show up in the cross reference list but had a ? instead of W or R to specify the type of access.
Usually, if you are protecting a block you should not use absolute addresses as it will be harder to keep control of the versioning.

One "artistic" way, I've seen to prevent this is a pointer to a DB as an input to the block. Mind you that it can be a pointer or may be an integer with the DB number and the logic inside the block creates the pointer from the DB number.

Check for block moves that affect that DB and check if the range goes past the addresses you have.
 
I was able to find an alternate location in the program, specifically a DB where the information from the HMI is stored.

I also found a corresponding FB written in STL(not my forte) where there were some references to address registers. I will plan to look more closely at it today, and sort out exactly what's going on there.

I have not worked with indirect addressing before, read a little bit about it. I am basically at the point now where I can work around it, but for the sake of getting better and learning, I'd like to figure out exactly how it works.

Thanks for all the help!
 

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