Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 12)

An Introduction to Programmable
Controllers
Chapter 2
2Ć5
In addition, the output section of modules with fuses has blown fuse indicators.
Typically, each output circuit is fused in the output section. Groups of these
fuses will have a blown fuse indicator associated with them. When one of the
fuses in the group opens, the blown fuse indicator will be lit.
Conditioning
The output section conditions the programmable controller’s signals for the
machine. that is, it converts the low-level DC voltages of the programmable
controller to the type of electrical power used by the output devices at the
machine.
Isolation
The output section isolates the more sensitive electronic circuitry of the
programmable controller from unwanted and dangerous voltages that
occasionally occur at the machine or the plant’s wiring system. There are
situations where additional external protection may be required.
Processor Section
The four major section of a programmable controller is the processor. The
processor section might be called the “brains” of the programmable controller
because it is divided into halves that serve functions similar to your brain. One
half is the Central Processing Unit (CPU), the other is memory.
Central Processing Unit
The Central Processing Unit (CPU) is divided into two sections:
Decision area - makes decisions about what the machine is to do.
Memory - storage area.
Memory
The programmable controller’s memory serves three functions:
Stores important information (or data) that the CPU may need to make its
decisions.
Stores sets of instructions called a program.
Stores
messages.
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Processor
Section
CPU
Data
Table
Program
Storage
Memory