xii C H A P T E R 6 PLC Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90 6.1 Creating PLC Ladder Logic Diagrams from Relay Logic Diagrams .....................................................................92 6.2 Programming Ladder Logic Diagrams with Normally Open and Normally Closed Switches .......................................................94 6.3 Programming Ladder Logic Diagrams with Normally Open and Normally Closed Contacts........................................................96 6.4 PLC Program Scan Time....................................................................99 6.5 PLC Program and Data Files........................................................... 100 6.6 Programming Ladder Logic Diagrams with Latch and Unlatch Instructions ..................................................................... 102 6.7 Loading and Troubleshooting PLC Ladder Diagrams in Run Mode................................................................................... 103 6.8 Using the PLC Force Instruction for Troubleshooting .................... 106 6.9 Creating and Printing PLC Program Reports ................................ 108 6.10 Using Utility Instructions to Save and Retrieve PLC Programs ............................................................................... 112 6.11 Using the LogixPro Simulator to Create Ladder Logic Diagrams.............................................................................. 114 C H A P T E R 7 Programming Logic Gate Functions in PLCs . . . . . . . . . . . . . . . 126 7.1 Combinational and Sequential Logic Gate Circuits ........................128 7.2 Boolean Expressions, Truth Tables, and Logic Gate Circuits.........128 7.3 NOT Gates (Inverters) .......................................................................129 7.4 AND Gates ......................................................................................... 130 7.5 OR Gates ............................................................................................ 131 7.6 NAND Gates ...................................................................................... 132 7.7 NOR Gates ......................................................................................... 134 7.8 XOR Gates.......................................................................................... 135 7.9 XNOR Gates....................................................................................... 136 7.10 Simplifying Boolean Expressions .................................................... 139 7.11 Creating PLC Ladder Logic Diagrams from Logic Gate Circuits ........................................................................ 145 7.12 Creating PLC Ladder Logic Diagrams from Boolean Expressions...................................................................... 149 7.13 Creating Logic Gate Circuits from PLC Ladder Logic Diagrams.............................................................................. 151 7.14 LogixPro Simulator Examples ........................................................ 153 6 7