Hi

Ok I know from the manuals that

:L KF +120
:T FW 14 load FW with the value "KF +120"
:DO FW 14
:L IB 0
before the operation "L IB" is executed,
the operand value ’0’ is replaced by the value
’120’;
Operation executed: L IB 120

but what if we had an operand value different from 0 like here

    L    FY 1
    L    KF +22
    XF   
    ADD    KF +41
    T    DW 2        // if FY1=0 -> DW 2 = 41 
    L    KF +4
    T    DW 3       //DW3 = 4
    L    KF +10
    T    DW 4       //DW4 =10

...

    DO    DW 3  // DW3 = 4
    L    IW 3       //  -> L IW ????
    DO    DW 2  //DW2 = 41
    T    DW 2     //T DW ??
    DO    DW 4  //DW4 = 10
    T    DW 4    // T DW ??

what should be done with  L IW 3 for example

PS these are my comments , correct me if Im wrong

Best Regards

Hello Zeyad;

Have a look at these documents, they should help you understand indexed addressing in S5 CPUs (DO instruction) and indirect addressing in S7  PLCs.

https://support.industry.siemens.com/tf/WW/en/posts/do-instruction-in-s5-converting-to-s7/16631?page=0&pageSize=10

Why are the bit and byte addresses changed when indirectly addressing a program converted from S5 to S7?

What is the difference between STEP 7 and STEP 5 with regard to the operations for indirect addressing?

Hope this helps,

Daniel Chartier

Hi Daniel,

Thx for your reply , I have seen some of these examples and i have no problem with finding my way in S7 , but new to S5

the problem that all examples after a DO the L or T operand is always 0 , whereas in this example it is different than 0, just want an explanation or example for such a case.

thanks

Zeyad_Rashed

Hi Daniel,

Thx for your reply , I have seen some of these examples and i have no problem with finding my way in S7 , but new to S5

the problem that all examples after a DO the L or T operand is always 0 , whereas in this example it is different than 0, just want an explanation or example for such a case.

thanks

 Hello,

Take a look at this post

https://support.industry.siemens.com/tf/ww/en/posts/s5-do-instruction/66480?page=0&pageSize=10

Kind regards,

BV