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B3 FUNCTION BLOCK DETAILS
B3.1 Eight Input OR Block
An eight input logical OR block whose output is high (1, On) if any one or more inputs is high (1, On). If more
than eight inputs are required, a second block is automatically introduced, as shown in Figure B.2. The blocks
in the figure are given the names 'A' and 'B', where 'A' and 'B' can be any of the 12 available instances.
OR blocks are used automatically by the 'user wiring' when more than one source is wired to the same
destination parameter. For example, it may be required that Relay (Digital I/O 2A2B) is to operate if channel 1
alarm 1 and/or channel 2 alarm 1 channels goes active. In such a case, the 'Active' parameter for the two
channel alarms would be wired to the same relay's 'PV' parameter.
OR blocks are invisible to the user interface, but the iTools graphical wiring page for this configuration (Figure
B.3), shows that an OR block has been introduced to OR the two alarm outputs together.
September 18
FEC920: USER GUIDE
Figure B.2 Eight input OR block
Figure B.3 iTools representation of OR block usage
A5E45696052A Rev-AA
Appendix B
Page 219
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