Lesson 7 Structuring a PLC Program

What is the purpose of an Allocation List in a PLC system?

• To define the programming language used

• To map inputs and outputs in the system

• To create a user interface for the PLC

• To store historical data of the PLC

Answer explanation

The purpose of an Allocation List in a PLC system is to map inputs and outputs, ensuring that each input and output device is correctly identified and configured for the control processes.

Which of the following is an example of an input device in a PLC?

• Temperature sensor

• Solenoid

• Light

• Motor

Answer explanation

A temperature sensor is an input device in a PLC as it measures environmental conditions and sends data to the controller. In contrast, a solenoid, light, and motor are output devices that perform actions based on the PLC's commands.

In PLC addressing, what does 'I' represent?

• Internal

• Instruction

• Input

• Interface

Answer explanation

In PLC addressing, 'I' stands for 'Input', which refers to the signals or data received from external devices. This distinguishes it from other options like 'Internal' or 'Instruction', which have different meanings.

What does the AND gate output when all inputs are 1?

• 0

• Error

• 1

• Undefined

Answer explanation

An AND gate outputs 1 only when all its inputs are 1. Since all inputs are 1 in this case, the output is 1, making it the correct choice.

Which addressing format groups inputs and outputs in bytes?

• Hex-Addressing

• Bit-Addressing

• Word-Addressing

• Byte-Addressing

Answer explanation

Byte-Addressing groups inputs and outputs in bytes, making it the correct choice. Unlike Bit-Addressing (which uses bits) and Word-Addressing (which uses words), Byte-Addressing specifically focuses on byte-sized data.

What is the output of a NOT gate when the input is 1?

• Error

• Undefined

• 0

• 1

Answer explanation

A NOT gate inverts the input signal. If the input is 1, the output will be 0. Therefore, the correct answer is 0.

Which function is used to compare two binary numbers?

• XOR

• OR

• NAND

• AND

Answer explanation

The XOR function compares two binary numbers by returning 1 for differing bits and 0 for matching bits. This makes it ideal for determining if two binary numbers are equal or different, hence it is the correct choice.

What is the first step in creating an Allocation List?

• Assign addresses

• Label devices

• Identify all devices

• Check compatibility

Answer explanation

The first step in creating an Allocation List is to identify all devices. This ensures you have a complete overview of what needs to be allocated before proceeding with labeling, assigning addresses, or checking compatibility.

In Omron PLC addressing, what does 'M' indicate?

• Motor control

• Manual input

• Memory or internal bits

• Main module

Answer explanation

In Omron PLC addressing, 'M' stands for Memory or internal bits, which are used for storing data and controlling logic operations within the PLC. This distinguishes it from other options like motor control or manual input.

What is the output of an OR gate if all inputs are 0?

• 1

• Undefined

• Error

• 0

Answer explanation

An OR gate outputs 1 if at least one input is 1. If all inputs are 0, the output is 0. Therefore, the correct answer is 0.