Ladder and STL as picture

vorapob

Dear Experts,

I use PLC S7-1500 I wondered about Ladder and STL as picture.

Why in Ladder the bit %DBX213.0 is red color but when in STL it normal color?

Best Regards,

It is a design choice from Siemens. The use of indirect and direct addressing is discouraged. When you compile the code the compile message states that the LAD network is not compatible with the S7-1500.

The assumption is made that a designer knows about the increased risk when STL code is used. Legacy designs are accommodated when code is built on STL. The STL runs on an 'emulator' mode; simulating the working of the legacy processors. This include registers and addressing methods. 

The optimized processing is only possible when the code set is migrated away from the STL code base. But that means some effort is needed to use the S7-1500 instruction set to deliver the equivalent working.

vorapob

Dear Experts,

I use PLC S7-1500 I wondered about the INPUT_ACTUAL int Data type why it can't use %DBW214.

How to fix it please ?

Best Regards,

It is the same situation as what we spoke about before. One solution is to have all the code in STL. Another solution is to push the %DBW214 into a temporary INT tag with SCL and then work accordingly.

It is a good idea to move all the data tags into a UDT structure and then work with the localized tags that has symbols.

Another concept that is more compatible with how the S7-1500 works, is to not use the OPN instruction. DB_ANY or DB handover by UDT parameter are two options. It is impossible to know which would be best when not seeing all the original code.