Rockwell Automation 1766-Lxxxx MicroLogix 1400 Programmable Controllers User Manual - Manual (Page 122)

80 Rockwell Automation Publication 1766-UM001H-EN-P - May 2014
Chapter 5 Using the LCD
File and download your application program to the controller. The TUF element
can only be changed by a program download.
The value stored in the TUF element identifies the double integer file with which
the LCD will interface. Valid double integer files are L9, and L10 through L255.
When the LCD reads a valid double integer file number, it can access up to 256
words (0 to 255) on the LCD screen. The protection bit (LCD edit disable) in
the data file properties of target integer file are used to define the read-only or
read/write privileges for its file.
Valid file type include Bit, Integer, Double integer or Float, as specified in the
TUF element.
The data protection for its file depends on the setting for LCD Edit Disable. If
LCD Edit Disable is set to 1 in file properties, the corresponding data file is
considered read-only by the LCD and the "Protected!" message is displayed.
For explanations in this section, we assume the following in the application
program:
• A bit file L9, which is 256 elements long (256 words), is defined with the
preset data, as shown in the screen capture below.
IMPORTANT Although you cannot change protected data from the LCD keypad, the
control program or other communication devices do have access to
this data. The Protection bit (LCD Edit Disable) only provides write
protection from the LCD keypad. This does not provide any overwrite
protection from ladder logic, HMI, or programming software. It is the
user’s responsibility to ensure that data is not inadvertently
overwritten.