Chapter 23 Computer System Vocabulary
Computer
A complex set of electrical circuits that, in an automobile, produce programmed electrical control currents for actuators after receiving specific input signals from sensors.
Processing
A computer's comparison of sensor inputs to data and operating ranges in its memory to determine a course of action.
Local Interconnect Network (LIN)
A data bus system that is designed to work in conjunction with CAN.
Buffer
A device that can serve as a temporary storage area for data and prevent improper data from entering internal computer chips.
Controller Area Network (CAN)
A high-speed computer data bus that can be used by several computers and sensors at the same time to communicate with each other.
Reference Voltage (Vref)
A known voltage (usually 1-5V) fed to passive sensors by a computer. Changes in sensor resistance can then be read by the computer as a change in current.
Relay
A magnetically operated switch that enables low current in one circuit to control (close or open) a greater current flow in a second circuit.
Multiplexing
A method of using one communications path to carry two or more signals simultaneously.
Binary Numerical System
A number system that uses two numbers (0 and 1) arranged in different sequences to represent other numbers, letters, words, computer input data, computer output data, or a condition.
Random Access Memory (RAM)
A portion of computer memory that serves as temporary storage for data. This data is lost if power to the computer is lost. It is used to store sensor information and diagnostic trouble codes.
Programmable Read Only Memory (PROM)
A semiconductor chip that contains instructions that are permanently encoded into the chip. Instructions contain base operating information for how a system's components should operate under various conditions.
Passive Sensor
A sensor that changes an externally produced signal, but does not generate its own voltage.
Analog Signal
A signal that can have a continuous range of strength.
Integrated Circuit (IC)
A single chip of semiconductor material that contains various electrical components in miniaturized form.
Servo Motor
A small dc motor actuator that can produce a rapid spinning motor when energized by a relay or main computer.
Digital Electronics
A specialized field of electronics that encompasses the ways in which a computer uses logic gates and the binary numbering system to make complex decisions (outputs) based on specific facts (inputs).
Circuit Sensing
A system that uses a computer instead of dedicated sensors to monitor current flow through various components and circuits.
Shielded Twisted-Pair Conductor
A twisted-pair conductor encased in a metal shield for greater electromagnetic interference reduction.
Flash Erasable Programmable Read Only Memory (FEPROM)
A type of ECM memory that contains vehicle operation data. It is normally reprogrammed father than replaced.
Read Only Memory (ROM)
A type of computer memory that stores permanent data that cannot be removed from memory. It contains the general information to operate a computer.
Electrically Erasable Programmable Read Only Memory (EEPROM)
A type of memory module in which the programming can be changed by scan tools and other electronic equipment that burns-in the new programming.
Erasable Programmable Read Only Memory (EPROM)
A type of microprocessor whose programming can be altered only by erasing it with special equipment and reprogramming.
Potentiometer
A variable resistor with three external connections that can be used to adjust voltage in a circuit.
Input
An electrical signal of a vehicle condition that is received and used by a computer.
Solenoid
An electrically operated magnetic device used to operate some unit. An iron core is placed inside a coil. When electricity is applied to the coil, the iron core centers itself in the coil and, as a result, it will exert some force on anything it is connected to.
Digital Signals
An electronic signal that uses on and off (or high-low) pulses.
Storage
Collection of programming, data, operating parameters, trouble codes, and other information that a computer accumulates and remembers on its memory chips.
Ring Configuration
Computer network configuration in which each computer is wired in series, or in a loop.
Star Configuration
Computer network configuration in which one main processing computer and several less complex computers work as a network.
Bus Configuration
Computer network configuration in which several of the vehicle's computers are wired to a signal conductor, or bus.
Active Sensor
Computer sensor that generates its own voltage signal in response to a change in a condition.
Output
Computer-produced electrical signals that are sent from a computer after processing input data.
Conditioner
Device that changes signals for use by other chips and circuits in a computer. It can be used to transform an analog sensor signal into a digital signal that a computer would understand.
Vehicle Sensor
Device that detects a physical operating change of a vehicle and converts it into an electrical signal for computer use. It can also be called a transducer.
Computer Signal
Electrical impulse or frequency used to carry electronic data.
Display Device
Electronic screen that shows output information in a dash instrument cluster(s) of an automobile. It includes vacuum-fluorescent, liquid-crystal and plasma displays.
Voltage Regulator
Electronic semiconductor device that manages the voltage and current output of an alternator.
Adaptive Strategy
Feature in an ECM that allows it to adjust its operation to compensate for sensor, actuator, or vehicle deterioration.
Gate
Indented metal part mounted on a shift rail. It aids in locking a shift fork into the correct synchronizer during gear shifts. Also, an electronic circuit that produces a specific output for a given input.
Signal Amplitude
Level of voltage present in a wave. High-amplitude signals have more voltage than low-amplitude signals.
Parallel Communication
Means of computer network communication that involves the use of several wires to exchange multiple bits of data simultaneously.
Serial Communication
Means of computer network communication that use only one wire to exchange digital data. In this setup, data is transferred one bit at a time.
Data Bus
Pathway for data inside a computer. It can also be used to refer to a circuit used to connect two on-board computers.
Computer Network
Series of computers that each control specific systems, but communicate and work as one to improve overall vehicle efficiency.
Computer System Block Diagram
Simple service manual drawing that uses shapes (squares, rectangles) and lines to display the interaction of sensors, actuators, and a computer.
Cybernetics
Study of how electrical and mechanical mechanisms can mimic the actions of the human body.
Duty Cycle
The percentage of "on" time for a device that is pulsed on and off.
Waveform
The shape of a given voltage over a period of time. It can be graphed with an oscilloscope or a scan tool with a scope function.
Pulse Width
The speed of a voltage signal change over time. High frequency signals have a short pulse width and low frequency signals have a long pulse width.
Transduce
To change from one form to another.
Single-Wire Conductor
Type of conductor with one insulated wire that carries data signals between computers.
Twisted-Pair Conductor
Type of conductor with two insulated wires that are wound, or twisted, into a spiral to carry data signals between computers.
Actuator
Type of motor that converts an electronic signal into movement or motion.
Differential Voltage Signal
Voltage signal used with twisted-pair conductors that consists of two complementary digital signals with opposing polarities.
Shielded Wire
Wire with a flexible metal tube around the conductor to block interference.
Keep Alive Memory (KAM)
a type of computer memory that stores changes in sensor values. It provides information to a computer's CPU so it can properly adjust signals to various output devices. It is sometimes referred to as adaptive strategy.
