Stupid Step7 Question

How does one create a FB call in LAD? I have added the FB75 "RMC75FB". The inputs and the outputs are ok but I get a red question mark above the FB. I know that this is supposed to be a DB but how is it entered and how is it created. From what I remember the DB was supposed to be created from the static data in FB75.
I haven't done this in three years. There must be some magic key stroke or place to click that allows me to create the DB75.

Thanks.

Peter-
You should be able to left double click on the red question marks and enter a DB number. In the cases I have done this the DB did not exist before I entered it above the FB call. I'm not sure what happens if you enter a DB that already exists. Step7 should create the DB for you out of the data structure entered in the FB, assuming you have at least one IN, OUT or STATIC data declaration.

Hope this helps,
Keith

Oh, its the secret left double click...

Now how am I supposed to guess that? Programming Step7 has been like playing Myst. I try this, click on that until I get the response I want.

I managed to find another way of doing it by creating an instance DB where I had to specify FB75 as the associated FB.

If Siemens could only make their Step7 easier to used I think Rockwell would have some competition. Until then.... Ah it will never happen. Step7 programmers, I salute you, your patience anyway for I have little.

Thanks Keith.

Re: Oh, its the secret left double click...

Peter Nachtwey said:

Now how am I supposed to guess that?

Click to expand...

Peter,

That is all part of the 'fun' and another reason why PLC's.net exists.

Enjoy your 're-learning' curve with Step7.

I won't make a comment on your reference to Rockwell otherwise this thread will turn into a 'my PLC is better than your PLC' thingy.

The one reason why I voted for 'familiarity' in Steve's poll

Paul

More Stupid Step7 Questions.

The Step7 writers are screwing with our minds. They leadeth us down long menus just to find all options are grayed out. I feel like a rat in the maze.

Now for the question. How does one modify the instance Data Block. I can delete it and recreate it but there must be an easier way.

BTW, Keith, left double click does not create or change the datablock. I just lets you enter in the name of a previously created data block.

Re: More Stupid Step7 Questions.

Peter Nachtwey said:

Now for the question. How does one modify the instance Data Block. I can delete it and recreate it but there must be an easier way.

Click to expand...

Peter,

What do you mean by 'modify' the instance DB? Do you mean you wish to edit the values within the DB? If this is the case then I am afraid that you cannot do this. These values (either pre-set or actual) are set by the FB associated with the instance DB, the only way to 'adjust' the preset values is by changing the values used in the FB, you cannot do this in the DB.

I think I have have explained that right.

I feel like a rat in the maze.

Click to expand...

I am sure that rats only have to escape a maze once, then they know their way.

paul

Hi Peter-
I'm running Step7 V5.1 SP3.
I have a small test program I just toseed together. It has OB1 and an FB1 I made up. FB1 has no logic, just various data declarations.
In ladder view in OB1 I insert a rung, go to the catalog (View -> Catalog), select 'FB' and drag FB1 to the rung. The block appears with the three red ? above it. I left click (sorry, double not required) the red question marks and an entry box appears. I type in 'db20' for example, which previously did not exist. I get a pop-up box that tells me the instance data block does not exist; do I want to create it. I click 'yes' and it's a done deal.
If I modify FB1 after I put the original call in OB1, my instance data block entry over FB1 will go red in OB1. If I right click on the instance data block entry a pop-up window will appear telling me the timestamp of the instance data block and the FB don't agree; do I want to regenerate the instance data block. If I say yes the same data block is re-created. The downside to this is any data that was put in there between the time it was originally created and the time it is re-created will get whacked.

Keith

PS:
You can modify actual values in an instance data block the same way you modify any other data block. Again, the issue is that if you need to regenerate an instance data block because the data structure changed, all of your actual data will be reset to the default values you entered in the FB.

There are lots of dead rats everywhere I look.

I am reading profibus data into a FB. I needed to change the array of profibus data to a structure. The FB has changed and passed the consistency check but the DB75 associated with the FB75 I just changed has not changed. When I view the data it is not in the right format. I think I am just going to delete it and create it again.

I just deleted the DB75 and created it again but it still has the arrays like the old FB75 did. I need to create a new DB75 that matches the UDTS in the new FB75. How does one do this?

I used to play a game called Adventure. "There are a lot of tiny twisty tunnels and they all look the same". Talk about frustration.

Hi Peter-
I think I just did what you are talking about.
I created a user defined data type (UDT1) with a mix of data types. I then used UDT1 as a static element in my FB1 data structure. I saved FB1. I went to OB1 and saved and got the red instance data block indication over my FB1 call. I right-click the red instance DB field and get the pop-up telling me to regenerate the data block. I do and the DB now contains the UDT I added.
I think it all starts with making sure the data structure in your FB is what you want. This is the master for what the DB will look like. At the very least, if you are modifying the DB directly, the FB data structure needs to exactly match the DB data structure.

Keith

kamenges said:

PS:
You can modify actual values in an instance data block the same way you modify any other data block. Again, the issue is that if you need to regenerate an instance data block because the data structure changed, all of your actual data will be reset to the default values you entered in the FB.

Click to expand...

Keith

Thanks for putting me right on that score, I have always been under the impression that you could not modify the DB values, at least that is the impression that Siemens support gave me.

Peter, I take it back about the rats, maybe there will be a few more dead ones along the way

Paul

Stupid Step7

I just right clicked the three red ??? and I get a get a pop up but there no option for generating a DB.

The options are:
Called Block->
Paste
Delete
Insert Network
Insert Empty Block
Insert Symbol
Go to Location
Edit Symbols

So what am I supposed to do? Wave a wand or say xyzzy?

I remember doing something like that with version 5.0 but I have version 5.1 now.

Phil you can't edit a instance DB directly. You can edit other types.
If I could edit the instance DB directly I would and I wouldn't be having this problem.

I solved this puzzle.

I closed the project and re-opened it again. Then is told me the DB75 was old and had a time conflicted and asked me to regenerate it. Now it is OK. What a pain. "plugh"

Sorry Pete-
I'm talking about two things at once and we are a bit out of phase here.
If you have the three ? on the screen you wil want to left click and enter a DB number (like DB75). You can enter either a whole new DB or a pre-existing DB. If it is a DB that doesn't exist you should get a prompt that says it doesn't exist and it will ask you if you want to generate it. If the DB already exists you should get a prompt that tells you the time stamps don't match and do you want to regenerate it.
The whole right-click thing applies to cases where you already have a valid function block call with a valid instance DB entered and saved somewhere in the program. In this case, if you go to the called FB and change the data structure in the FB, the assigned instance DB is no longer valid. When you save the called FB it will tell you the interface has changed and you may be screwwed. Just save it and go on.
At this point if you try to save the block that calls the FB the instance DB field will still contain the previously entered DB number but the field will turn red. this is where the right-click deal will bring up a window asking you to regenerate the instance DB.

I hope this helps. Granted, Step7 is pretty cryptic. It doesn't automatically update stuff for you like Logix5000 does when you change a structure. With Step7 you have to go through and update all the instances yourself manually.

Keith

kamenges said:

I hope this helps. Granted, Step7 is pretty cryptic. It doesn't automatically update stuff for you like Logix5000 does when you change a structure. With Step7 you have to go through and update all the instances yourself manually.

Keith

Click to expand...

Keith, I am pretty sure that I did the consistency check on all the moduled I modified 3 or 4 times. Step7 didn't seem to catch the fact that DB75 was out of date until is saved and closed the project and exited Step7 and then restarted Step7 and reloaded the project again.

That, too, sounds like Step7.
I have to admit I've run across several instances (pardon the word) where Step7 got into a state I couldn't get out of. There are still a few I'm not real sure how I recovered from.
What I don't quite get is why the added steps. If you change the data structure in an FB, why doesn't Step7 pop up a list of the calls affected and ask you to either OK the DB update or enter a new DB? It seems to me you will be forced to do this anyway. Why not help you out?

Keith