1. Chapter 11
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2. 11.1
Math Instructions
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3. The PLC’s math functions capability allows it to perform arithmetic functions on values.
Addition - The capability to add one piece of data to
another.
Subtraction - The capability to subtract one piece of
data from another.
Multiplication - The capability to multiply one piece
of data by another.
Division - The capability to divide one piece of data
by another.
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4. When the CPT (compute) instruction is executed, then copy, arithmetic, logical, or conversion operation residing in the expression field of this instruction is performed and the result is sent to the destination.
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5. 11.2
Addition Instruction
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6. The ADD instruction performs the addition of two values stored in the referenced memory locations.
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7. Simulated ADD instruction rung.
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8. Counter program that uses the ADD instruction.
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9. Simulated counter program.
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10. Carry (C) - Address S2:0/0, is set to 1 when there is
The arithmetic status bits for the SLC 500 are found in word 0, bits 0 to 3 of the processor status file S2.
Carry (C) - Address S2:0/0, is set to 1 when there is
a carry in the ADD instruction or a borrow in the SUB
instruction.
Overflow (O) -Address S2:0/1, is set to 1 when the
result is too large to fit in the destination register.
Zero (Z) - Address S2:0/2, is set to 1 when the result
of the subtract instruction is zero.
Sign (S) - Address S2:0/3, is set to 1 when the result
is a negative number.
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11. Subtraction Instruction
11.3
Subtraction Instruction
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12. The subtract instruction subtracts source B from source A and stores the result in the destination.
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13. Simulated SUB instruction rung.
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14. Vessel overfill alarm program.
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15. Simulated vessel overfill alarm program.
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16. Multiplication Instruction
11.4
Multiplication Instruction
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17. The multiply instruction multiplies two values and stores the result in the destination address.
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18. Simulated MUL instruction rung.
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19. MUL instruction program used to calculate the product of two sources.
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20. Simulated MUL instruction program used to calculate the product of two sources.
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21. The MUL instruction used as part of a temperature control program.
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22. 11.5
Division Instruction
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23. The division instruction divides the value in source A by the value in source B and stores the result in the destination address.
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24. Simulated DIV instruction rung.
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25. DIV instruction used to calculate the value that results from dividing source A by source B.
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26. Simulated DIV instruction program.
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27. Program for converting Celsius temperature to Fahrenheit.
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28. Other Word-Level Math Instructions 11.6
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29. Square root instruction.
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30. Simulated square root instruction rung.
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31. The negate (NEG) instruction changes the sign of the source value from positive to negative.
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32. Simulated negate instruction rung.
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33. The clear (CLR) instruction sets all bits of a word to zero.
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34. Simulated clear instruction rung.
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35. The convert to BCD (TOD) instruction is used to convert 16-bit integers into binary-coded decimal (BCD) values.
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36. Simulated convert to BCD (TOD) instruction rung.
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37. The result, 377, is placed in the destination address, N7:1.
The scale data (SCL) instruction is used to allow very large or very small numbers to be enlarged or reduced by the rate value.
The number 100 stored at the source address, N7:0, is multiplied by 25,000, divided by 10,000, and added to 127.
The result, 377, is placed in the destination address, N7:1.
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38. File Arithmetic Operations
11.7
File Arithmetic Operations
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39. The file arithmetic and logic (FAL) instruction can combine an arithmetic operation with file transfer.
The file add function of the FAL instruction is used to perform addition operations on multiple words.
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40. The file subtract function of the FAL instruction is used to perform subtraction operations on multiple words.
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41. The file multiplication function of the FAL instruction is used to perform multiplication operations on multiple words.
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42. The file divide function of the FAL instruction is used to perform division operations on multiple words.
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