Chapter 4. Ladder Diagram (LD) ProgrammingGFK-2950C February 2018 754.2.6 Logical AND, Logical OR, and Logical XOREach scan that power is received, the Logical function examines each bit in bit string IN1 and thecorresponding bit in bit string IN2, beginning with the least significant bit in each. You can specify astring length of 1 to 256 WORDs or DWORDs. The IN1 and IN2 bit strings specified may overlap.Logical ANDIf both bits examined by the Logical AND function are 1, AND places a 1 in the corresponding locationin output string Q. If either bit is 0 or both bits are 0, AND places a 0 in string Q in that location.AND passes power flow to the right whenever it receives power.Tip: You can use the Logical AND function to build masks or screens, where only certain bits arepassed (the bits opposite a 1 in the mask), and all other bits are set to 0.Logical ORIf either bit examined by the Logical OR function is 1, OR places a 1 in the corresponding location inoutput string Q. If both bits are 0, Logical OR places a 0 in string Q in that location. The functionpasses power flow to the right whenever it receives power.Tips:■ You can use the Logical OR function to combine strings or to control many outputs with onesimple logical structure. The Logical OR function is the equivalent of two relay contacts in parallelmultiplied by the number of bits in the string.■ You can use the Logical OR function to drive indicator lamps directly from input states or tosuperimpose blinking conditions on status lights.Logical XORWhen the Exclusive OR (XOR) function receives power flow, it compares each bit in bit string IN1with the corresponding bit in string IN2. If the bits are different, a 1 is placed in the correspondingposition in the output bit string.For each pair of bits examined, if only one bit is 1, then XOR places a 1 in the corresponding locationin bit string Q. XOR passes power flow to the right whenever it receives power.Tips for Logical XOR■ If string IN2 and output string Q begin at the same reference, a 1 placed in string IN1 will causethe corresponding bit in string IN2 to alternate between 0 and 1, changing state with each scanas long as power is received.■ You can program longer cycles by pulsing the power flow to the function at twice the desiredrate of flashing. The power flow pulse should be one scan long (one-shot type coil or self-resetting timer).■ You can use XOR to quickly compare two bit strings, or to blink a group of bits at the rate of oneON state per two scans.■ XOR is useful for transparency masks.
