S7-1500 Instance DB addressing

treellama · Nov 16, 2017

I'm porting some Tia Portal V14 code from an S7-300 cpu to an S7-1500. I have a couple places where I've moved an input word (for example IW400

) to a UDT, so that I can pick bits out of it that have real labels. I do this in a ladder FB, with UDT's in the static declarations.

My old code just MOV'd IW400

to %DIW0
but that syntax doesn't work anymore.

Likewise, if I try to access that address directly (for example DB321.DBW0), it says that address doesn't exist. It looks like I can do it as P#DB321.DBX0.0 but I'm not sure why. If I needed my FB to be multi-instance, I'm not sure how I would do it.

Any explanations out there from the experts?

mk42 · Nov 16, 2017

treellama said:
I'm porting some Tia Portal V14 code from an S7-300 cpu to an S7-1500. I have a couple places where I've moved an input word (for example IW400) to a UDT, so that I can pick bits out of it that have real labels. I do this in a ladder FB, with UDT's in the static declarations.

My old code just MOV'd IW400 to %DIW0
but that syntax doesn't work anymore.

Likewise, if I try to access that address directly (for example DB321.DBW0), it says that address doesn't exist. It looks like I can do it as P#DB321.DBX0.0 but I'm not sure why. If I needed my FB to be multi-instance, I'm not sure how I would do it.

Any explanations out there from the experts?

In the 1500 you use a tag, instead of worrying about the addresses. Symbolic everything is the key. If you already have a UDT created, then you're halfway there.

Create a tag in the tag table of type [Your UDT] starting at bit I400.0. Create a tag in your instance DB also of that type. Move INPUT_TAG (or INPUT_TAG

) to INSTANCE_TAG.

The other thing you can do to make bit access easy is to use "slice addressing". Access TAGNAME.X0 for the least significant bit, TAGNAME.X32 for the MSB of a double word, TAGNAME.B1 for the 2nd byte, etc. It takes care of all the byte swapping for you.

S7-1500 Instance DB addressing

treellama

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mk42

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