Message Display - Basic Operations

You can use a variable to select and display a predefined message with a message display.

A message display can have up to 20000 states. Each state can have a predefined message. The maximum number of states that a message display can have is determined by the state type and data type of the monitored variable. The following table shows the maximum in each case.

		Type of Variable	Maximum
State Type	Bit	Bit	2
	Value	16-bit	256
		32-bit	256
	LSB	16-bit	17
		32-bit	33
	Value as string number	16-bit	20000
		32-bit	20000

If the state type is Bit or Value or LSB, you need to specify the number of states for a message display, and the number must not exceed the allowed maximum. You can set the text (message) for each state. At runtime, a message display shows the message corresponding to the state of the monitored variable. The state of the monitored variable is determined by the state type and value of the variable.

If the state type is Value as string number, you need to select a text table and specify the first and last string number in the text table for a message display. And the string number must not exceed the allowed maximum. At runtime, a message display shows the message corresponding to data value of the monitored variable. The data value specifies intended string number in a pre-designated text table.

For example:

Text Table A is selected. The string number range is from 1 to 100

Data Value	String Number	State	String ID	Comment
0	0	Invalid		No string is identified.
5	5	5	A00005
200	200	Invalid		Out of range. No string is identified.

Note: The differences between Message Display and Lamps are:

Lamps can display either text or picture, or both; while message display can only display text. Both message displays and lamps can display predefined text by changing the value of the monitored variable. However, only message displays can perform as a marquee that is controlled by the value of the monitored variable and a specified running speed.

You can complete all the settings of a message display in the Message Display dialog box. This dialog box contains the following four pages. Some of the pages appear only when they are needed.

■ General
Described in Section 6.3.4.

■ Text
Described in Section 4.3.6.

■ Visibility
Described in Section 4.4.6.

■ External Label
Described in Section 4.3.8.