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Chapter 5. Function Block Diagram (FBD)
5.3.1
Logical AND, Logical OR, and Logical XOR
The Logical functions examine each bit in bit string IN1 and the corresponding bit in bit string IN2,
beginning with the least significant bit in each string, and places the result in Q. If additional inputs
(IN3 up to IN8) are used, the function compares each bit in the input with the corresponding bit in Q
and places the result in Q. The comparison is repeated for each input that is used. The input bit
strings specified in IN1 ... IN8 may overlap.
Minimum number
of inputs = 2
Maximum number
of inputs = 8
240
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
Logical AND
If both bits examined by the Logical AND function are 1,
AND places a 1 in the corresponding location in output
string Q. If either bit is 0 or both bits are 0, AND places a 0 in
string Q in that location.
Tip:
You can use the Logical AND function to build masks
or screens, where only certain bits are passed (the
bits opposite a 1 in the mask), and all other bits are
set to 0.
Minimum number of inputs = 2
Maximum number of inputs = 8
Logical OR
If either bit examined by the Logical OR function is 1, OR
places a 1 in the corresponding location in output string Q. If
both bits are 0, Logical OR places a 0 in string Q in that
location.
Tips:
▪
You can use the Logical OR function to combine strings
or to control many outputs with one simple logical
structure. The Logical OR function is the equivalent of
two relay contacts in parallel multiplied by the number
of bits in the string.
▪
You can use the Logical OR function to drive indicator
lamps directly from input states or to superimpose
blinking conditions on status lights.
GFK-2950C
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