Chapter 5. Function Block Diagram (FBD)GFK-2950C February 2018 2555.8.2 Move DataWhen the input operand, EN, is set to ON, the MOVE instruction copies data asbits from one location in PACSystems controller memory to another. Because thedata is copied as bits, the new location does not need to use the same type ofmemory area as the source. For example, you can copy data from an analogmemory area into a discrete memory area, or vice versa.MOV sets its output, ENO, whenever it receives data unless one of the following occurs:▪ When the input, EN, is set to OFF, then the output, ENO, is set to OFF.▪ When the input, EN is set to ON, and the input, IN, contains an indirect reference, and thememory of IN is out of range, then the output, ENO, is set to OFF.The value to store at the destination Q is acquired from the IN parameter. If IN is a variable, the valueto store in Q is the value stored at the IN address. If IN is a constant, the value to store in Q is thatconstantThe result of the MOVE depends on whether the data type for the Q operand is a bit reference or anon-bit reference:▪ If Q is a non-bit reference, LEN (the length) indicates the number of memory locations in whichthe IN value should be repeated, starting at the location specified by Q.▪ If Q is a bit reference, IN is treated as an array of bits. LEN therefore indicates the number of bitsto acquire from the IN parameter to make up the stored value. If IN is a constant, bits arecounted from the least-significant bit. If IN is a variable, LEN indicates the number of bits toacquire starting at the IN location. Regardless, only LEN bits are stored starting at address Q.For example, if IN was the constant value 29 and LEN is 4, the results of a MOV operation are asfollows:▪ Q is a WORD reference: The value 29 is repeatedly stored in locations Q, Q+1, Q+2, and Q+3.▪ Q is a BOOL reference: The binary representation of 29 is 11101. Since LEN is 4, only the fourleast-significant bits are used (1101). This value is stored at location Q in the same order, so 1 isstored in Q, 1 is stored in Q+1, 0 is stored in Q+2, and 1 is stored in Q+3.If data is moved from one location in discrete memory to another, such as from %I memory to %Tmemory, the transition information associated with the discrete memory elements is updated toindicate whether or not the MOVE operation caused any discrete memory elements to change state.Note: If an array of BOOL-type data specified in the Q operand does not include all the bits in abyte, the transition bits associated with that byte (which are not in the array) are clearedwhen the Move instruction receives data.Data at the IN operand does not change unless there is an overlap in the source and destination—asituation that is to be avoided.
