Hi to all

I resd about peripheral address and I understood their performance

But what I still don't understand is how to define these addresses on module?

And when we specify size of  PII ,PIQ , how do we know that peripheral  address is in range?

and how we know How much capacity of pII  is used?

BEST REGARD

Hi behnam ba,

the difference between process image and peripheral I/O is very important when programming a PLC. It is always good to understand it.

Since it looks to me like you are new to programming a SIMATIC PLC, a little digression on the process image of these controllers. The S7 (S7-300/S7-400) was introduced at a time when memory was comparatively small and expensive. Therefore these controllers have only a limited amount of memory for the process image. With the current controllers of the S7-1200/S7-1500 family, it is no longer necessary to consider the process image. The process image covers the entire addressable area.

The addresses of the individual modules can be defined as described in chapter 2.3.8 of the programming and operating manual "SIMATIC Configuring Hardware and Communication Connections STEP 7". In the first generations there was no possibility to freely assign the address (for local modules). The following definition was used. Starting from the first possible slot for signal modules, the start addresses for digital modules are assigned starting from zero with a distance of 4. Analog modules start at address 256 with a distance of 16. This definition is still used today for automatic assignment, but the addresses can be adapted in the meantime.

In the hardware editor (HW Config) you can use the address overview (menu "View > Address overview ... CTRL+U) to get a list of all addressed modules. The column "PIP" shows if a process image is used or not. Unfortunately I do not know a way to show the load of the process image.

Kind regards
Stefan

Hi stefan 

best regard

behnam ba

Hi stefan 

I read the article, but I still did not get the answer to my questions

Please provide more detail

 Stefan already answered your questions.

when we use the address overview (menu "View > Address overview ... CTRL+U) to get a list of all addressed modules ,this does not give me size Used of PII and PQI

What are the advantages and disadvantages of using peropheral addresses?

behnam ba

What are the advantages and disadvantages of using peropheral addresses?

 You can access IO with peripheral addresses during the program execution, before a new cycle starts, when inputs states are read.

In the 300/400 plc series, the size of the process image is not the full area you can address. If you have I/O devices outside of the Process image size, you can access the I/O through peripheral address.

Hi behnam ba,

the manual "CPU 31xC and CPU 31x: Technical specifications" describes the advantages of the process image as follows (see chapter "Address areas of the system memory"):

Access to the process image, compared to direct access to the input/output modules, offers the advantage that a consistent image of process signals is made available to the CPU during cyclic program processing. If the signal state at an input module changes during program execution, the signal status in the process image is maintained until the process image is updated in the next cycle. Moreover, since the process image is stored in the CPU's system memory, access to the process image is significantly faster than direct access to the signal modules.

For newer PLC, the size of the process image can be adjusted. The list of CPUs that support this can be found in the chapter above. However, the default size is 256, as was the fixed size for older CPUs. The size of the process image for your specific CPU can be found in the technical data. Unfortunately, I don't know how to see the process image load, and I'm pretty sure the software doesn't provide an option for that.

Kind regards
Stefan

Hi stefan

thank you very much in did

behnam