Many thanks for your efforts. Alas, this is not actually what I am looking for. Like I said, the system has many displays, some with 4 digits, some with many more characters. This is why the first function I suggested takes as parameters a string as a source, and a start address and byte count as destination. Now imagine I want to use your design. It has 5 fixed output bytes, so assuming the displays had just 5 characters, I would have to connect all of the 5 bytes for each display, which is a pain, isn't it?

In order to write a generic function for all displays that performs well, I just need a way to transfer a string to output memory with a single instruction (without loops), and to clear the remaining bytes also with a single instruction, on a S7-1200 CPU, which apparently does not support POINTER and the like.

William_B

Have a PEEK at this design example / idea..

rdiez2005

....

How do I implement it with Strg_TO_Chars()? I have an S7-1200 CPU. I want to call it like this:

CopyStringToOutputData( DisplayStartAddress := 123, DisplayByteCount := 5, Text:= "12345" );

Keep in mind that I have more than 10 displays connected, so there will be many different calls like that.

By the way, I haven't figured out how yet to convert the device ID/whatever to the start memory address (the 123 above) and the data length (the 5 above). Unfortunately, RD_ADDR ist not supported on SIMATIC S7-1200 with firmware versions older than 4.0.0, which is what I have, and I did not want to use absolute addresses.

 You want two separate things here. With Strg_TO_Chars you can convert a string into an array of bytes.

The second thing is to send this array to your Profinet device which depends very much on the characteristics of your device.  E.g. if it has normal I/O mapped to it, you could use POKE_BLK with the area_dest set to 16#82.

Hi!

Sorry for your disappointment!

I did read your first and all other comments. Have you read mine?

In the last post I mentioned that POKE_BLK will work with area_dest = 16#82, so you can write to the outputs.

If you put your byte array, containing the ascii codes of your string in a shared DB, it can be moved to the output bytes. Indeed, it is not as nice as moving the array from the local stack,  but that is not possible.

William_B

Commentary made by Kahl about POKE_BLK is truthful.
This is the way to go.

Step7 module under TIA Portal V13 SP1
offers some more commands and functionality
with S7-1200 FW4.1 hardware for example.

Thanks for your help. Unfortunately, we still have TIA Portal v12 and my development CPU is a SIMATIC S7-1200 which apparently cannot be upgraded to Firmware version 4, because the hardware only supports version 3.0.

From what I gathered further above, POKE_BLK cannot copy directly from a string or array on the stack (local memory), but there may be a way to copy first from stack to a DB, and then from DB to output memory. This is a waste of DB memory as a temporary buffer, but it should work (I haven't tried it yet on my system).

Alternatively, you are suggesting Strg_TO_Chars() to local (stack) memory and then MOVE_BLK_VARIANT. I am not sure that Strg_TO_Chars() is necessary, as you can declare an overlayed array with AT mapped over the string. The S7-1200 has limitations with VARIANT, but MOVE_BLK_VARIANT might still work.

If I understand it correctly, for MOVE_BLK_VARIANT to work, the customer has to define in the global tag table an array tag with the right size for each display (depending on the size of the display's output memory). This would have to be done manually.

Is there a way to avoid having to declare such a global array tag per display? There are functions (as mentioned in this thread) to retrieve the I/O addresses from a module ID. The idea is that the function gets the module or submodule ID as a parameter and automatically finds the output data address.

Is it possible to declare in SCL a byte array mapped (maybe an overlay with AT) at a certain data output address? In TIA Portal, for a given function block, the AT overlay syntax seems to be limited to overlaying the previous variable. From what I heard, constructiong a VARIANT at an arbitrary address (given as a function parameter) may not be possible on the S7-1200, because this CPU does not really support indirect addressing well.

I never thought that something like this could be so hard with Siemens systems. There is a mess of device families and firmware versions with various levels of incompatibilities that makes your life really hard. I wonder whether this mess is actually on purpose.

rdiez2005

If I understand it correctly, for MOVE_BLK_VARIANT to work, the customer has to define in the global tag table an array tag with the right size for each display (depending on the size of the display's output memory). This would have to be done manually.

Is there a way to avoid having to declare such a global array tag per display? There are functions (as mentioned in this thread) to retrieve the I/O addresses from a module ID. The idea is that the function gets the module or submodule ID as a parameter and automatically finds the output data address.

Just for the record, I just realised that declaring an array in the global tag table is not possible. Even using a user-defined data type does not seem to work. Global tags can only be of simple, built-in types like DINT. POKE and POKE_BLK may indeed be the only way.