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Programmable Interval Timer
In computing and in embedded systems, a programmable interval timer (PIT) is a counter that generates an output signal when it reaches a programmed count. The output signal may trigger an interrupt. Common features PITs may be one-shot or periodic. One-shot timers will signal only once and then stop counting. Periodic timers signal every time they reach a specific value and then restart, thus producing a signal at periodic intervals. Periodic timers are typically used to invoke activities that must be performed at regular intervals. Counters are usually programmed with fixed intervals that determine how long the counter will count before it will output a signal. IBM PC compatible The Intel 8253 PIT was the original timing device used on IBM PC compatibles. It used a 1.193182 MHz clock signal (one third of the color burst frequency used by NTSC, one twelfth of the system clock crystal oscillator, therefore one quarter of the 4.77 MHz CPU clock) and contains three timers. Timer 0 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intel 8253
The Intel 8253 and 8254 are programmable interval timers (PITs), which perform timing and counting functions using three 16-bit counters. The 825x family was primarily designed for the Intel 8080/ 8085-processors, but were later used in x86 compatible systems. The 825x chips, or an equivalent circuit embedded in a larger chip, are found in all IBM PC compatibles and Soviet computers like the Vector-06C. In PC compatibles, Timer Channel 0 is assigned to IRQ-0 (the highest priority hardware interrupt). Timer Channel 1 is assigned to DRAM refresh (at least in early models before the 80386). Timer Channel 2 is assigned to the PC speaker. The Intel 82c54 (c for CMOS logic) variant handles up to 10 MHz clock signals. History The 8253 is described in the 1980 Intel "Component Data Catalog" publication. The 8254, described as a superset of the 8253 with higher clock speed ratings, has a "preliminary" data sheet in the 1982 Intel "Component Data Catalog". The 8254 is implem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embedded System
An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is embedded as part of a complete device often including electrical or electronic hardware and mechanical parts. Because an embedded system typically controls physical operations of the machine that it is embedded within, it often has real-time computing constraints. Embedded systems control many devices in common use. , it was estimated that ninety-eight percent of all microprocessors manufactured were used in embedded systems. Modern embedded systems are often based on microcontrollers (i.e. microprocessors with integrated memory and peripheral interfaces), but ordinary microprocessors (using external chips for memory and peripheral interface circuits) are also common, especially in more complex systems. In either case, the processor(s) us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Random Access Memory
Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' " power") or dynamic may refer to: Physics and engineering * Dynamics (mechanics), the study of forces and their effect on motion Brands and enterprises * Dynamic (record label), an Italian record label in Genoa Mathematics * Dynamical system, a concept describing a point's time dependency ** Topological dynamics, the study of dynamical systems from the viewpoint of general topology * Symbolic dynamics, a method to model dynamical systems Social science * Group dynamics, the study of social group processes especially * Population dynamics, in life sciences, the changes in the composition of a population * Psychodynamics, the study of psychological forces driving human behavior * Social dynamics, the ability of a society to react to changes * Spiral Dynamics, a social development theory Other uses * Dynamics (music), the softness or loudness of a sound or note * DTA Dynamic, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NE555
The 555 timer IC is an integrated circuit used in a variety of timer, delay, pulse generation, and oscillator applications. It is one of the most popular timing ICs due to its flexibility and price. Derivatives provide two ( 556) or four ( 558) timing circuits in one package. The design was first marketed in 1972 by Signetics and used bipolar junction transistors. Since then, numerous companies have made the original timers and later similar low-power CMOS timers. In 2017, it was said that over a billion 555 timers are produced annually by some estimates, and that the design was "probably the most popular integrated circuit ever made". History The timer IC was designed in 1971 by Hans Camenzind under contract to Signetics. In 1968, he was hired by Signetics to develop a phase-locked loop (PLL) IC. He designed an oscillator for PLLs such that the frequency did not depend on the power supply voltage or temperature. Signetics subsequently laid off half of its employees due t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monostable Multivibrator
A multivibrator is an electronic circuit used to implement a variety of simple two-state devices such as relaxation oscillators, timers, latches and flip-flops. The first multivibrator circuit, the astable multivibrator oscillator, was invented by Henri Abraham and Eugene Bloch during World War I. It consisted of two vacuum tube amplifiers cross-coupled by a resistor-capacitor network. They called their circuit a "multivibrator" because its output waveform was rich in harmonics. A variety of active devices can be used to implement multivibrators that produce similar harmonic-rich wave forms; these include transistors, neon lamps, tunnel diodes and others. Although cross-coupled devices are a common form, single-element multivibrator oscillators are also common. The three types of multivibrator circuits are: # Astable multivibrator, in which the circuit is not stable in either state —it continually switches from one state to the other. It functions as a relaxation oscillator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Precision Event Timer
The High Precision Event Timer (HPET) is a hardware timer available in modern x86-compatible personal computers. Compared to older types of timers available in the x86 architecture, HPET allows more efficient processing of highly timing-sensitive applications, such as multimedia playback and OS task switching. It was developed jointly by Intel and Microsoft and has been incorporated in PC chipsets since 2005. Formerly referred to by Intel as a Multimedia Timer, the term HPET was selected to avoid confusion with the software multimedia timers introduced in the MultiMedia Extensions to Windows 3.0. Older operating systems that do not support a hardware HPET device can only use older timing facilities, such as the programmable interval timer (PIT) or the real-time clock (RTC). Windows XP, when fitted with the latest hardware abstraction layer (HAL), can also use the processor's Time Stamp Counter (TSC), or ACPI Power Management Timer (ACPI PMTIMER), together with the RTC to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel
The Linux kernel is a Free and open-source software, free and open source Unix-like kernel (operating system), kernel that is used in many computer systems worldwide. The kernel was created by Linus Torvalds in 1991 and was soon adopted as the kernel for the GNU operating system (OS) which was created to be a free software, free replacement for Unix. Since the late 1990s, it has been included in many Linux distributions, operating system distributions, many of which are called Linux. One such Linux kernel operating system is Android (operating system), Android which is used in many mobile and embedded devices. Most of the kernel code is written in C (programming language), C as supported by the GNU compiler collection (GCC) which has extensions beyond standard C. The code also contains assembly language, assembly code for architecture-specific logic such as optimizing memory use and task execution. The kernel has a Modular programming, modular design such that modules can be inte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LAPIC
In computing, Intel's Advanced Programmable Interrupt Controller (APIC) is a family of programmable interrupt controllers. As its name suggests, the APIC is more advanced than Intel's 8259 Programmable Interrupt Controller (PIC), particularly enabling the construction of multiprocessor systems. It is one of several architectural designs intended to solve interrupt routing efficiency issues in multiprocessor computer systems. The APIC is a split architecture design, with a local component (LAPIC) usually integrated into the processor itself, and an optional I/O APIC on a system bus. The first APIC was the 82489DX it was a discrete chip that functioned both as local and I/O APIC. The 82489DX enabled construction of symmetric multiprocessor (SMP) systems with the Intel 486 and early Pentium processors; for example, the reference two-way 486 SMP system used three 82489DX chips, two as local APICs and one as I/O APIC. Starting with the P54C processor, the local APIC functionality was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PC Speaker
A PC speaker is a loudspeaker built into some IBM PC compatible computers. The first IBM Personal Computer, model 5150, employed a standard 2.25 inch magnetic driven (dynamic) speaker. More recent computers use a tiny moving-iron or piezo speaker instead. The speaker allows software and firmware to provide auditory feedback to a user, such as to report a hardware fault. A PC speaker generates waveforms using the programmable interval timer, an Intel 8253 or 8254 chip. Use cases BIOS/UEFI error codes The PC speaker is used during the power-on self-test (POST) sequence to indicate errors during the boot process. Since it is active before the graphics card, it can be used to communicate "beep codes" related to problems that prevent the much more complex initialization of the graphics card to take place. For example, the Video BIOS usually cannot activate a graphics card unless working RAM is present in the system while beeping the speaker is possible with just R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft Windows
Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sectors of the computing industry – Windows (unqualified) for a consumer or corporate workstation, Windows Server for a Server (computing), server and Windows IoT for an embedded system. Windows is sold as either a consumer retail product or licensed to Original equipment manufacturer, third-party hardware manufacturers who sell products Software bundles, bundled with Windows. The first version of Windows, Windows 1.0, was released on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces (GUIs). The name "Windows" is a reference to the windowing system in GUIs. The 1990 release of Windows 3.0 catapulted its market success and led to various other product families ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, packaged as a Linux distribution (distro), which includes the kernel and supporting system software and library (computing), libraries—most of which are provided by third parties—to create a complete operating system, designed as a clone of Unix and released under the copyleft GPL license. List of Linux distributions, Thousands of Linux distributions exist, many based directly or indirectly on other distributions; popular Linux distributions include Debian, Fedora Linux, Linux Mint, Arch Linux, and Ubuntu, while commercial distributions include Red Hat Enterprise Linux, SUSE Linux Enterprise, and ChromeOS. Linux distributions are frequently used in server platforms. Many Linux distributions use the word "Linux" in their name, but the Free ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Counter (digital)
In digital electronics, a counter is a sequential logic circuit that counts and stores the number of positive or negative transitions of a clock signal. A counter typically consists of flip-flop (electronics), flip-flops, which store a value representing the current count, and in many cases, additional logic to effect particular counting sequences, qualify clocks and perform other functions. Each relevant clock transition causes the value stored in the counter to increment or decrement (increase or decrease by one). A digital counter is a finite state machine, with a ''clock'' input signal and multiple output signals that collectively represent the state. The state indicates the current count, encoded directly as a binary number, binary or binary-coded decimal (BCD) number or using encodings such as one-hot or Gray code. Most counters have a ''reset'' input which is used to initialize the count. Depending on the design, a counter may have additional inputs to control functions suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
