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ECP (Extended Capabilities Port)
An asynchronous, 8-bit-wide parallel channel defined by IEEE 1284-1944 that provides PC-to-peripheral and peripheral-to-PC data transfers.
EEPROM (Electrically Erasable Programmable Read-Only Memory)
ROM that can be erased with an electrical signal and reprogrammed.
Embedded System
A combination of computer hardware and software, and perhaps additional mechanical or other parts, designed to perform a dedicated function. In some cases, embedded systems are part of a larger system or product, as is the case of an anti-lock braking system in a car. Contrast with general-purpose computer.
Encoder
A feedback device which converts mechanical motion into electronic signals. Usually an encoder is a rotary device that outputs digital pulses which correspond to incremental angular motion. The encoder consists of a glass or metal wheel with alternating clear and opaque stripes that are detected by optical sensors to produce the digital outputs.
Energize
Instruction that causes a bit to be a one. This turns an output on.
Ethernet
The standard for local communications networks developed jointly by Digital Equipment Corp., Xerox, and Intel. Ethernet baseband coaxial cable transmits data at speeds up to 10 megabits per second. Ethernet is used as the underlying transport vehicle by several upper-level protocols, including TCP/IP.
Expansion rack
A rack added to a PLC system when the application requires more modules than the main rack can contain. A remote rack is sometimes used to permit I/O to be remotely located from the main rack.
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