298 Programable logic controllers/ Lesson 3 Programming the System

At this point, you know that a PLC program is a list of ____? to the processor.

Instructions

Rung comments are part of what is known in programming as ____? documentation.

internal

Rung comments are part of a PLC's ___?, and can be a great help to Programmers and maintenance personnel.

internal documentation

An output will generally only be on one rung in a program. If it is energized by several sets of conditions, they will appear as ___? on the input side of the rung.

Branches

If a switch is connected to a particular PLC input terminal and the switch is closed, the processor writes that information into the input image table as a binary ___? If that switch is open, then a binary #___? is written into the table. Remember, all the inputs are read and recorded at the ____?of a scan.

1,0, beginnin

Each manufacturer of programmable controllers using a Boolean language has a stack register with a given number of levels. Some systems might have a stack with four levels, others might have six, still others might have eight or 16 levels. Even the most complex logic can be done with only___? levels.

4

Even the most complex logic can be assembled with a maximum of ___? levels in a stack register.

4

Series logic is represented by the Boolean ___? function.

AND

Parallel logic is represented by the Boolean ___? function.

OR

The PLC's ____? is an obedient and faithful direction follower. Unless the processor itself fails, it simply executes the instructions, one at a time, over and over.

Processor

You are trying to control the outputs so that the overall PLC process takes place in the way it was intended. It is the ___? that "connects" the inputs and outputs.

Program

First we will examine how a typical PLC operates. The PLC processor continuously runs the same program loop, called the?

Scan

The PLC processor continuously runs a program loop called a?

Scan

What does stack register FILO stand for

First bit in last bit out (FILO)

A ___? signal is used to coordinate several programs within a single operation.

Handshaking

Separate programs can coordinate with the total operation through the use of a ____? signal

Handshaking

We need something to tell our plc program when to start its sequence. That something is called a ____? signal.

handshake

In ladder logic the output instruction that looks like a coil is called output___?

energize

A robot begins its program in a preset position called the ___? position.

home

It is a ____? loop system in that the outputs do affect the input. Even so, it is the outputs that are being controlled. The inputs are the feedback needed to tell the operator when the output has done its job.

closed

Rung comments are a part of external documentation true or false?

false they are internal

The processor "reads" the inputs. At the beginning of every scan, the processor "looks" at its input modules and writes the current condition of every input into a scratch table in its memory. That table is called the ____? table and is part of the files ____? discussed earlier.

input image files, data files

Construction of a PLC program begins with analyzing the process to be controlled. You will need to know the____? of____? and all the inputs and outputs involved in the process.

sequence, operations

The PLC names INPUT LIMIT SWITCH and OUTPUT CONTROL RELAY below the instructions. These names are called____? or____? and can be used to identify the device more quickly and easily than by their address.

symbols, tags

The OR statement rule explains how the OR statement works with the ___? statement.

load

The OR statement rule is as follows: each time an OR statement is used, that statement is combined with the previous ____? statement.

load

A PLC program connects the inputs and outputs___ ?

logically

There is no physical or electrical connection between the inputs and outputs. The user-entered program connects them "____ ."

logically

According to the OR statement rule, each time an OR statement is used, it is combined with the previous load statement True or False?

True

The processor updates the outputs. Only after it has finished evaluating every line in the program does the processor actually tell the outputs what they should do based on this most recent review of the user program. This step is known as ____? the output image table. The real world outputs are not updated until the entire user program has been ____?

writing, evaluated

In terms of relay logic, normally closed contacts are referred to with the Boolean term .

NOT

It is important to remember that PLC____? are nothing more than a list of logical instructions for the processor to follow.

Programs

To help identify devices more quickly and easily thab by their addresses, a programmer often assigns___?

Tags

what register is a software device that aids in the assembly of programming logic.

The Stack Register

step1=The process of writing a PLC program might seem complicated until you realize that programs are simply lists of logical instructions. The program executes these instructions over and over. The processor runs the same program loop, called the scan, which consists of three basic steps. First, the processor reads the inputs and writes their condition to the___?

input image table

The PLC processor executes the user program. In this middle step, the processor looks through the program, the list of instructions the programmer has put into its memory. It starts at the top of the list (the first rung of the ladder) and works through each rung until it gets to the end. In this process, it uses the information it just wrote in the ____ ____? table to help it determine which outputs should be turned on and which ones should be turned off. But it does not change any of the outputs yet—it simply jots them down in its ____?

input image, memory

We use a stack to put together complex logic. The more complex the logic, the more___? are used. With The FILO stack rule Each time a LOAD instruction is used, the logic is___?___? one level into the stack. Each time an AND LOAD or OR LOAD instruction is entered, the logic is___?___? one level. AND LOAD and OR LOAD instructions are used to combine groups of logic in AND fashion and OR fashion respectively.

levels, Pushed down, pulled up

Boolean logic, unlike ladder logic, is not a graphical language. It is written in the form of a ?

listing form

Boolean logic is not a graphic language but is written in the form of a ___?. It is based on the principles of Boolean algebra. Series logic is represented by the Boolean ___? function, parallel logic is represented by the ___?function, and normally closed contacts are referred to with the term ___?. All logic is some combination of these three logical operations. The stack register is a software device that helps assemble complex logic. Each time a LOAD instruction is used, the logic is pushed ___?one level into the stack. Each time an AND LOAD or OR LOAD instruction is entered, the logic is pulled ___? one level in the stack.

listing, AND, OR, NOT, DOWN, UP

Step2=. Next the processor executes the user program. Finally the processor updates the outputs, also known as writing the ___?___?___?. When programming a PLC, remember that you are trying to control the outputs. You need feedback to tell you when the output has done its job. It is at this time that you need to consider the inputs.

output image table

It is the PLC ____? that causes something to take place in that machine or process in the real world.

outputs

Whenever the PLC is put in the ____?mode, it runs this program loop.

run