This document discusses system programming and implementation. It begins by outlining steps for defining the control task and developing a control strategy, including thinking through the solution before programming. It then provides guidelines for programming, such as understanding the desired function, flowcharting the process, and assigning I/O addresses. The document outlines programming guidelines for new applications and modernizations. It stresses organizing the program and choosing the correct hardware and software. Flowcharting is described as a way to represent and communicate the operational process sequentially using standard symbols. Pseudo code is presented as an alternative to flowcharts.

1. System Programming
and Implementation

2. Control Task Definition
 Begin by defining the control task, I.e.
determine what needs to be done.
 Sometimes an outline of the steps to be
performed will assist in defining the task.
 Sketches of process flow and major
equipment can also assist in the definition.
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3. Control Strategy
 The key to defining the strategy is:

THINK FIRST, PROGRAM LATER
 Planning a solution of the sequence of
steps that must occur in the program to
produce the desired output control.
 This step is also called developing an
Algorithm.
 Algorithm is a set of procedures that define a
problem.
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4. Implementation
Guidelines
 Techniques used to implement control
programs vary with the
programmer, nevertheless, certain
guidelines should be followed as follows:
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5. Programming
Guidelines
New Application
 Understand the desired function of the
system.
 Review possible control methods and
optimize the process operation.
 Flowchart the process operation.
 Implement the flowchart by using logic
diagrams or relay logic symbology.
 Assign real I/O addresses and internal
addresses to inputs and outputs.
 Translate the logic implementation into
PLC code or structured text language.
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6. Programming
Guidelines





Modernizations
Understand the actual process or machine
function.
Review machine logic of operation and
optimize when possible.
Assign real I/O and internal addresses to
inputs and outputs.
Translate relay ladder diagram into PLC
coding.
Translate relay ladder diagram to
structured text code if required. (optional)
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7. Program Organization
and Implementation
 Organization is a key when programming
and implementing a control solution. The
larger the project, the more organization
is needed, especially when a group of
people are involved.
 Success also depends on the ability to
implement it. The programmer must
understand the control task and controlled
devices, choose the correct equipment for
the job (hardware and software) and
understand the control system.
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8. Flowcharting
 A Flowchart is a pictorial representation
that records, analyzes and communicates
information, as well as describes the
operational process in a sequential
manner.
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9. Some Flowchart
Symbols
Process
A group of one or more instructions that
Perform a processing function
Input / Output
Any function involving an input/output device
Decision
A point in the program where a branch to
alternate paths is possible

10. Some Flowchart
Symbols
Preparation
A group of one or more instructions that sets
the stage for subsequent processing
Predefined Process
A group of operations not detailed in the
flowchart (often a library subroutine)
Terminal
Beginning, end, or point of interruption in a
program
Connector
Entry from, or exit to, another part of the
flowchart

11. Simple Flowchart &
Pseudo Code
Pseudo code for the
same process
Assign preset values
If PB is pressed Then
Read analog input
Store read value in register
If temperature > 100°C Then
subroutine()
Else
Turn heater coil ON
Endif
Else
Wait for PB
Endif