Pick a string from the global constants

Store all the data in your HMI.  When you need data, set the "constant" index, and set a bool true that is only true when you want the HMI to send over the string.

Monitor that bool in your HMI.  Trigger a script that grabs the string, moves it to a PLC tag, and then toggles the bool.

In the PLC, it waits for the bool to go from hi to low, the uses the string sent over from the hmi.

If you find there is a delay in the string arriving, you can "constantly" move the string last sent from the HMI to another tag.  The HMI monitors what it sent with what is in the "holding" area and sets a bool when they match.  The PLC can monitor for that bool to know it has the entire string and can process it.  After processing, it can reset the "HMI data received" bool, and start the cycle over again for the next text.

For a more algorithm-based approach, you might consider a scheme where you have 2 DBs, 1 with a dictionary of all available "words" that make up all the "constant" string messages.  The other DB is a 2-dimensional array, where 1st dimension is say your 0.999, and the 2nd dimension handles the building of the string for that index

For example, let's say this is the constants you need to send for 3 different cases (for simplicity):

constant[0] : "SEND-TO:<user1@domain1>"
constant[1] : "Subject: PLC error # 12345"
constant[2] : "Message: This is a generic message with many words"

Dictionary DB could look like this:

Dictionary DB :Token : array[0.499] of string[10]

Dictionary.Token[0] = "SEND-TO"
Dictionary.Token[1] = ":"
Dictionary.Token[2] = "user1"
Dictionary.Token[3] = "@"
Dictionary.Token[4] = "<"
Dictionary.Token[5] = "domain1"
Dictionary.Token[6] = ">"
Dictionary.Token[7] = "Subject"
Dictionary.Token[8] = " "
Dictionary.Token[9] = "PLC"
Dictionary.Token[10] = "error"
Dictionary.Token[11] = "#"
Dictionary.Token[12] = "12345" // this is where a better algorithm
// could gain even more space savings
// by dynamically creating the error # strings
Dictionary.Token[13] = "Message"
Dictionary.Token[14] = "This"
Dictionary.Token[15] = "is"
Dictionary.Token[16] = "a"
Dictionary.Token[17] = "generic"
Dictionary.Token[18] = "message"
Dictionary.Token[19] = "with"
Dictionary.Token[20] = "many"
Dictionary.Token[21] = "words"
Dictionary.Token[22] = "From"
Dictionary.Token[23] = "To" 

The output string would get built based on the above token indexes.  Let's say the definition is defined something like this:

Constant.Def is [array[0.999] of array[0..25] of int] in general terms.  Note that using the last element of the int array is the NULL character (and building the output string can stop.

Not proper syntax. Just conveying the concept.

  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Constant.Def[0] = [00,01,04,02,03,05,06,00,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25]
Constant.Def[1] = [07,01,08,09,08,10,08,11,08,12,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25,25]
Constant.Def[2] = [13,01,08,14,08,15,08,16,08,17,08,18,08,19,20,08,21,25,25,25,25,25,25,25,25,25]

Create an FB that accepts the index for the constant, passing dictionary as InOut, Constant Definition array at that specific index, and outputs the built constant string using the tokens and the constant definition.

It would loop through the constant.def array row at index, using the array value as index into the dictionary.token array, concatenating token by token until the string is fully built, and spitting the final string out for using by your project. 

ing.lukic

#dP

What do you need the string for? If it is something that needs to be displayed on a (Siemens) HMI, other solutions may be available.

I need that for sending SMS. There will be predefined texts which will be sent to mobile phone(s). Which text - that will be sent from a WinCC Prof.

In fact - that will be alarms from the sistem which contains 60 PLC's. All alarms are olready collected in the WinCC. Each PLC sends alarms by 3-4 DW tags. Several alarms can occured in the same time. I am planing VB script to send ID number of the alarm text, based on tags analising. One PLC will take this number and place it in a FIFO memory (maybe no longer then 10 registers). On the other hand, PLC will be taking numbers from the FIFO and will be sending SMS to the phones. I was planing to avoid sending texts from the WinCC to the PLC. Money is limited and I was planing to by only CP 1242-7 V2.