Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual - Manual (Page 78)

Planning Your System Programs
Chapter 6
6-7
Once you identify the individual actions, you can add these actions to
your plan to complete your program. Once you have an SFC program that
defines the individual machine actions for your process, you can create a
ladder-logic program that controls the outputs of those machine actions. It
does not matter in what order you program these rungs. This program
merely contains the ladder logic that defines a command for each machine
action in your process.
Program Entry
When you finish your detailed analysis, you have your main program
planned. Now, enter your program into your terminal.
PLC-5 memory is divided into two areas: data and program-file storage.
Areas of Storage Description
Data All of the data the processor examines or changes is stored in files in data
storage areas of memory. These storage areas store:
• Data received from input modules
• Data to be sent to output modules; this data represents decisions made
by the logic
• Intermediate results made by the logic
• Preloaded data such as presets and recipes
• Control instructions
• System status
Program Files You create files for program logic, depending on the method you are using:
ladder logic, sequential function charts, and/or structured text. These files
contain the instructions to examine inputs and outputs and return results.
Data Table Memory
You can address data files in different formats when you write your
programs. Refer to Table 6.E for valid data table file-type specifications.
Addressing Data Table Files
DATA STORAGE
I/O Image Files
BlockĆTransfer Files
PROGRAM FILES
Examine Data Return Results
Input Output
Other Data Files
Data Data