Chapter 10 PLC Math Instructions Objectives Program the

Chapter 10 PLC Math Instructions

Objectives • Program the add instruction in the PLC ladder logic diagram. • Program the subtract instruction in the PLC ladder logic diagram. • Program the multiply instruction in the PLC ladder logic diagram. • Program the divide instruction in the PLC ladder logic diagram. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Addition • Add (ADD) instruction has three operands: – Two operands hold source data (Source A and Source B), which are added together. – Either both sources can be registers or one source can be a register while the other one is a number. – Third operand is the destination. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Addition (Cont. ) • Add instruction for Allen-Bradley SLC 500 series PLC displayed in block format. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Description of Status Bits © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Subtraction • Subtract (SUB) instruction has three operands: – Two operands, Source A and Source B, hold the source data. – Content of Source B is subtracted from Source A. – Result is placed in the destination. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Subtraction (Cont. ) • Subtract instruction for the Allen-Bradley SLC 500 series PLC displayed in block format. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Multiplication • Multiply (MUL) instruction has three operands: – Two operands hold the source data (Source A and Source B). – Either both sources can be registers, or one source can be a register while the other one is a number. – Destination must be a register. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Multiplication (Cont. ) • Multiply instructions in SLC 500 series PLCs displayed in block format. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Division • Divide (DIV) instruction has three registers: – Two registers hold the source data (Source A and Source B). – Either both sources can be registers or one source can be a register while the other one is a number. – Destination must be a register. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Division (Cont. ) • Divide instructions in SLC 500 series PLCs displayed in block format. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Advanced Math Instructions • Advanced math instructions are used to perform mathematical computations. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Advanced Math Instructions (Cont. ) • Compute (CPT) instruction may be used to solve mathematical equations. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Advanced Math Instructions Example • Given the following equation, you can use the CPT instruction to solve it. Y = (A × (ln B) × e. C) + (tan D) © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Advanced Math Instructions Example (Cont. ) • First assign floating point register locations for the parameters in the equation. • Note that integer registers such as N 7: 0 hold integer numbers. • Floating point registers such as F 8: 0 hold a real number that has both integer and fractional part. © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Advanced Math Instructions Example (Cont. ) • Assigned registers are: A = F 8: 0 B = F 8: 1 C = F 8: 2 D = F 8: 3 Y = F 8: 4 © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.

Advanced Math Instructions Example (Cont. ) • Normally open contact I: 1/0 is closed, equation in CPT instruction block calculated. • Result is placed in floating point register four (F 8: 4). © Goodheart-Willcox Co. , Inc. Permission granted to reproduce for educational use only.