Browse Definitions:
Definition

power-on reset (PoR)

Contributor(s): Stan Gibilisco

A power-on reset (PoR) is a circuit that provides a predictable, regulated voltage to a microprocessor or microcontroller with the initial application of power. The PoR system ensures that the microprocessor or microcontroller will start in the same condition every time that it is powered up.

A PoR system can be a peripheral, but in sophisticated processors or controllers the PoR is integrated on the main chip. The most basic PoR system can comprise a resistor and capacitor connected together with values tailored so that, when power is first applied, the capacitor takes a predictable and constant time to charge up. For computer use, however, additional components are often required, including a circuit called a Schmitt trigger. When the PoR circuit is designed, the charge-up time should be adjusted by trial and error so that all of the processor or controller circuits can set themselves to the correct initial values before the computer begins to function.

A well-designed PoR circuit can ensure that when power is applied to a computer, it will start up properly every time (or almost every time), and will never (or rarely) freeze up right away. This feature not only saves the user a great deal of frustration, but it offers a last resort in case of a stubborn system crash: the so-called cold boot, where the computer is completely powered-down for a minute or two, and then powered-up all over again.

 

Continue reading about power-on reset:

Maxim Integrated Products discusses PoR and related functions for processors.

Dr. Howard Johnson outlines common problems that can occur with poorly designed PoR circuits.

HyperPhysics describes how a Schmitt trigger works.

This was last updated in April 2012

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

-ADS BY GOOGLE

File Extensions and File Formats

SearchCompliance

SearchSecurity

  • Web application firewall (WAF)

    A Web application firewall (WAF) is a firewall that monitors, filters or blocks traffic to and from a Web application. WAFs are ...

  • MD5

    The MD5 hashing algorithm is a one-way cryptographic function that accepts a message of any length as input and returns as output...

  • identity theft

    Identity theft, also known as identity fraud, is a crime in which an imposter obtains key pieces of personally identifiable ...

SearchHealthIT

SearchDisasterRecovery

  • call tree

    A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...

  • mass notification system (MNS)

    A mass notification system is a platform that sends one-way messages to inform employees and the public of an emergency.

  • disaster recovery as a service (DRaaS)

    One approach to a strong disaster recovery plan is DRaaS, where companies offload data replication and restoration ...

SearchStorage

  • secondary storage

    Secondary storage is used to protect inactive data written from a primary storage array to a nonvolatile tier of disk, flash or ...

  • VRAM (video ram)

    VRAM (video RAM) is a reference to any type of random access memory (RAM) used to store image data for a computer display.

  • ZFS

    ZFS is a local file system and logical volume manager created by Sun Microsystems to control the placement, storage and retrieval...

SearchSolidStateStorage

  • SSD RAID (solid-state drive RAID)

    SSD RAID (solid-state drive RAID) is a methodology commonly used to protect data by distributing redundant data blocks across ...

  • Tier 0

    Tier 0 (tier zero) is a level of data storage that is faster, and perhaps more expensive, than any other level in the storage ...

  • PCIe SSD (PCIe solid-state drive)

    A PCIe SSD (PCIe solid-state drive) is a high-speed expansion card that attaches a computer to its peripherals.

SearchCloudStorage

  • RESTful API

    A RESTful application program interface breaks down a transaction to create a series of small modules, each of which addresses an...

  • cloud storage infrastructure

    Cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or ...

  • Zadara VPSA and ZIOS

    Zadara Storage provides block, file or object storage with varying levels of compute and capacity through its ZIOS and VPSA ...

Close