Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual - Manual (Page 14)

Understanding Your System
Chapter 1
1-4
Figure 1.2 illustrates a program-development model that you can use.
Figure 1.2
ProgramĆDevelopment Model
Functional
Specification
Detailed
Anaylsis
(General Conception)
Program
Testing
Acceptance
Development
SignĆoff
This model allows for the interaction of activities at the different levels.
Each section represents an activity that you perform. Prepare a functional
specification to start; then, prepare the detailed analysis.
Based on the detailed analysis, you can also develop your programs, enter
your programs, and test them. When testing is complete, you are ready to
implement the programs in your application. The detailed analysis can be
used as the basis for developing your testing procedures and requirements.
Because the functional specification is well thought out, it can be used as
the program sign-off document.
Functional Specification Content
The functional specification represents a very general view of your process
or a description of operation. Identify the events and the overall order in
which they must occur. Identify the equipment that you will need for your
process/operation. Generally indicate the layout of your system. If your
application requires a distributed control system, for example, indicate
where you will need remote I/O links. Also, you can have a process that is
located close to your processor. The process can require faster update time
than that provided by a remote I/O link, so you can select an extended-
local I/O link for that process.
Important: Choose a communication rate for your remote I/O link at
which every device on the link can communicate.