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The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a fieldbus or computer network that plugs into the PLC. The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control , distributed control systems , and networking .
PLA schematic example. A programmable logic array (PLA) is a kind of programmable logic device used to implement combinational logic circuits.The PLA has a set of programmable AND gate planes, which link to a set of programmable OR gate planes, which can then be conditionally complemented to produce an output.
An industrial control system (ICS) is an electronic control system and associated instrumentation used for industrial process control.Control systems can range in size from a few modular panel-mounted controllers to large interconnected and interactive distributed control systems (DCSs) with many thousands of field connections.
HCI—Human—Computer Interaction; HD—High Density; HDD—Hard Disk Drive; HCL—Hardware Compatibility List; HD DVD—High Definition DVD; HDL—Hardware Description Language; HDMI—High-Definition Multimedia Interface; HECI—Host Embedded Controller Interface; HF—High Frequency; HFS—Hierarchical File System; HHD—Hybrid Hard Drive
In 1969, Motorola offered the XC157, a mask-programmed gate array with 12 gates and 30 uncommitted input/output pins. [3] In 1970, Texas Instruments developed a mask-programmable IC based on the IBM read-only associative memory or ROAM. This device, the TMS2000, was programmed by altering the metal layer during the production of the IC.
Actuator Sensor Interface (AS-Interface or ASi) is an industrial networking solution (Physical Layer, Data access Method and Protocol) used in PLC, DCS and PC-based automation systems. It is designed for connecting simple field I/O devices (e.g. binary ON/OFF devices such as actuators, sensors, rotary encoders, analog inputs and outputs, push ...
Siemens SIMATIC S7-300 PLC CPU with three I/O modules attached. As with other programmable logic controllers, SIMATIC devices are intended to separate the control of a machine from the machine's direct operation, in a more lightweight and versatile manner than controls hard-wired for a specific machine. Early SIMATIC devices were transistor ...
The processors receive information from input modules, process the information and decide control actions to be signalled by the output modules. The field inputs and outputs can be analog signals e.g. 4–20 mA DC current loop or two-state signals that switch either "on" or "off", such as relay contacts or a semiconductor switch.