How to writte the bit of a local word of a FC?

Hello,

Here my problem;

I have a FC where I have defined an in/out local variable called Aux_Word

Now I would like to do something like

U "Any_Bool_Varible"

= Aux_Word.%x0

I think it is something like taht on TIA, but what about Simatic STEP 7? how could I do it?

Thanks!

alvconsan

Hello,

Here my problem;

I have a FC where I have defined an in/out local variable called Aux_Word

Now I would like to do something like

U "Any_Bool_Varible"

= Aux_Word.%x0

I think it is something like taht on TIA, but what about Simatic STEP 7? how could I do it?

Thanks!

 Hello.

• Declare 16 bits in the loal / temp declaration area.
  (temp_bit_0 .. temp_bit_15)
  
  
• Move Aux_Word into LW0
  
  
• Have the input bit (like "Any_Bool_Variable")
  interact with the temp bit.
  
  
• Move LW0 into Aux_Word.

L Aux_Word
T LW0 // populate local word 0

A "Any_Bool_Varible"
= #temp_bit_0

L LW0 // move back from local word 0
T Aux_Word

 
There are several other options, but I prefer this one. TIA however complains about using this idea. For that case it would be best to use WORD operations like WORD-AND.

Helpful?

Morning;

I don't understand 2 things;

-How could I select bit 3 (p.e) of the word?

- And I have never used a LW 0, Its taht a special variable? 

Could it be that the answer to both is taht, LW is a special variable and I can work with anysingle bit of that variable writting, LW 0 (bit 0 of the word), LW 1 (bit 1 of the word)...LW 15 (bit15 of the word)?

Thank you very much

alvconsan

Morning;

I don't understand 2 things;

-How could I select bit 3 (p.e) of the word?

- And I have never used a LW 0, Its taht a special variable? 

Could it be that the answer to both is taht, LW is a special variable and I can work with anysingle bit of that variable writting, LW 0 (bit 0 of the word), LW 1 (bit 1 of the word)...LW 15 (bit15 of the word)?

Thank you very much

The TEMP variable (tag) declaration area has a direct address. You can access this local area as L .. Lx.y   LBx   LWx   LDx     where x and y are numbers.

The direct addresses for the 16 bits would be L0.0 to L1.7. Note that L1.0 is the least significant bit. My suggestion is to declare symbols in the TEMP declaration:

temp08  bool
temp09  bool
...
temp15  bool
temp00 bool
...
temp07 bool

You will use temp03 as the symbol where you would have use Aux_Word.%X3.

LW0 would cover all the bits from L0.0 to L1.7 which is also covered by the 16 boolean temp** symbols.

Did that help?

alvconsan

Morning;

I don't understand 2 things;

-How could I select bit 3 (p.e) of the word?

- And I have never used a LW 0, Its taht a special variable? 

Could it be that the answer to both is taht, LW is a special variable and I can work with anysingle bit of that variable writting, LW 0 (bit 0 of the word), LW 1 (bit 1 of the word)...LW 15 (bit15 of the word)?

Thank you very much

 Hello alvconsan. 

LW stand for Local word, its Local because it is existing only on the local stack which is a shared memory area on the CPU that can be accessed by your code blocks, you find this memory area on the Temp declaration table on the interface of FBs and FCs. This area is initialized with each call, so at the beginning of FC,FB execution the Temp area is initialized. The values changes only take effect inside the FC and they are not remembered for next cycle.

You can see the absolute addresses on your local variables on temp declaration table and there you can address them like LB x, LW x, LD x, L x.x. Of course areas can overlap and with this you can select the bit, byte or word that you desire.

Regards.

Hello.

Rescobedo

This area is initialized with each call, so at the beginning of FC,FB execution the Temp area is initialized. 

The quoted statement is not true. We are not dealing with an S7-1200 or S7-1500 when working with Step7 Classic.

At first glance your reply does not offer more information than what I have already written. Perhaps my wording has been bad or perhaps you are offering helpful detail. Please consider highlighting what you add to the conversation. ..this is not my attempt to sarcasm.

Thanks for helping and engaging in conversation on this forum.
Well wishes.

My bad, you are right, I read again appendix in manual, it just states that values on local stack are overwritten. 

Regards.

Finally;