Rockwell-automation Logix5000 Controllers ASCII Strings Programming Ma Manuale Utente Scaricare il pdf (Pagina 16)

Chapter 1 Communicating with an ASCII device

Example:

When the temperature reaches the low limit (temp_low is on), the AWT instruction sends nine

characters from the string[2] tag to a MessageView terminal. (The $14 counts as one character. The

hex code for the Ctrl-T character.)

In the following example, you send a different number of characters each time and

want to automatically append one or two characters to the end of the data:

Example:

When alarm is on, the AWA instruction sends the characters in alarm_msg and appends a

termination character.

• Because the number of characters in alarm_msg varies, the rung first moves the length of

alarm_msg (alarm_msg.LEN) to the length of the AWA instruction (alarm_write.LEN).

• In alarm_msg, the $14 counts as one character. The hex code for the Ctrl-T character.

Send a different number of characters each time:

Example:

When MV_update is on, the AWT instruction sends the characters in MV_msg.

• Because the number of characters in MV_msg varies, the rung first moves the length of MV_msg

(MV_msg.LEN) to the length of the AWT instruction (MV_write.LEN).

• In MV_msg, the $16 counts as one character. The hex code for the Ctrl-V character.

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

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Rockwell-automation Logix5000 Controllers ASCII Strings Programming Ma Manuale Utente Pagina 16