Rockwell-automation Logix5000 Controllers ASCII Strings Programming Ma Manuale Utente Scaricare il pdf (Pagina 26)

Chapter 2 Processing ASCII characters

• The source is the same string tag as for the FIND instruction.

• The quantity values tells the MID instruction how many characters to pull

from the source.

• The start value is the same as the Result value from the FIND instruction.

This tells the MID instruction where to start pulling characters from the

Source.

• The Destination contains the characters you located.

The following example builds a string that contains two variables. For example, an

operator terminal may require a string that looks like the following:

• For more variables, use additional INSERT or CONCAT instructions.

• If you must send a floating-point value, use a RTOS instruction in place of

the DTOS instruction.

• The final string excludes the termination character. When you send the

string, use an AWA instruction to automatically append the termination

character.

Example:

To trigger a message in a MessageView terminal, the controller sends the terminal a message in this

format: [Ctrl-T] message # \ address [CR]

Important:

When send_msg is on, the rung does the following:

− The first DTOS instruction converts the message number to ASCII characters.

− The INSERT instruction inserts the message number (in ASCII) after the control character

[Ctrl-T]. (The hex code for Ctrl-T is $14.)

− The second DTOS instruction converts the node number of the terminal to ASCII characters.

− The CONCAT instruction puts the node number (in ASCII) after the backslash [ \ ] and stores

the final string in msg.

Important:

To send the message, an AWA instruction sends the msg tag and appends the carriage return

[CR].

Build a string

26 Rockwell Automation Publication 1756-PM013D-EN-P - October 2014

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Rockwell-automation Logix5000 Controllers ASCII Strings Programming Ma Manuale Utente Pagina 26