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Key Point:
If the screen does not change as expected
If the screen is changed from the PLC, and the GT main unit function switch parts are also used to
change the screen (Change Screen operation mode), a case sometimes occurs in which the screen
does not change, even though an instruction to change the screen has been issued by the PLC.
Example:
Screen No. 1 is displayed in keeping with the instruction from the PLC, and the screen is changed to
Screen No. 2 using the function switch parts.
This problem can be solved in the following manner:
Use the "forced-display flag" in the basic communication area/bit device.
1. At the same time that the PLC issues an instruction to change the screen again to Screen No. 1, or
shortly after that point, the forced-display flag in the first word/Bit E of the basic communication area/bit
device is turned on, using the bit as a PLC bit operation instruction.
2. When the forced-display flag begins to go on, the screen corresponding to the number written to the
first word of the basic communication area/word device, meaning Screen No. 1, is forcibly displayed at
the point that step 1 takes place. (This is carried out only at the rise of the forced-display flag).
Set the operation mode of the function switch parts to "Value Set".
When the screen is switched using the function switch parts, as shown in the illustration above, the
operation mode of the function switch parts is set to "Value Set" in order to switch the screen.
Using the "Value Set" mode changes the contents of the first word in the basic communication area/word
device (the screen number specified by the PLC) and the third word (the number of the currently
displayed screen) to that of the new screen number, and thus avoids the kind of case described above.
6-5
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