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Standard Mode
Section 4-6
4.6.6
PLC-Handshake
Handshake handling:
-
If the terminal writes to a variable for which the PLC handshake option has been
selected, the RA bit (refresh request bit) in the Read coordination byte will be set
and data entry inhibited.
-
The PLC can now, for example, provide a new data set for other input variables.
The PLC will then set the RQ bit (refresh acknowledgement bit) in the Write
coordination byte.
-
Once the operating terminal detects that the RQ bit has been set, the terminal
reads every input variable contained in the currently selected mask from the
PLC again, then allows data inputs again and resets the RA bit.
-
If the RQ bit is already set when writing to the variable for which the PLC hand-
shake option has been selected, then the other input variables will be refreshed
immediately and data entry will not be inhibited.
Fig. 11: Pulse diagram - PLC handshake
4.6.7
Refreshing One-Time Output Data
To refresh input or one-time output variables (variables are read only once and are
displayed) that a mask contains, simply reactivate the mask (external mask selec-
tion).
Summary of Contents for NT15S
Page 1: ...Cat No V056 E1 1 Programmable Terminal NT4S NT15S NT18S OPERATION MANUAL ...
Page 2: ...ii ...
Page 3: ...iii NT4S NT15S NT18S Programmable Terminal Operation Manual Produced March 1999 ...
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Page 14: ...xiv ...
Page 26: ...12 The Terminals of the NT Series Section 1 2 1 2 4 1 2 NT4S SF122B E 1 2 4 1 3 NT4S SF123B E ...
Page 37: ...23 The Terminals of the NT Series Section 1 4 1 4 1 3 NT4S SF123B E 1 4 1 4 NT15S SF121B E ...
Page 54: ...40 The Terminals of the NT Series Section 1 7 1 7 6 3 ASCII Character Set Table ...
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