Legacy Plug and Play

Source: Wikipedia, the free encyclopedia.
The sound card Sound Blaster AWE32 PNP CT3990 had a Plug-and-Play ISA Bus interface chip (large square chip, mid of bottom row).

The term Legacy Plug and Play,

IBM PC standard bus, later dubbed Industry Standard Architecture (ISA). Related specifications are also defined for the common external or specialist buses commonly attached via ISA at the time of development, including RS-232 and parallel port
devices.

As a Windows feature, Plug and Play refers to operating system functionality that supports connectivity, configuration and management with native plug and play devices.[4] Originally considered part of the same feature set as the specifications, Plug and Play in this context refers primarily to the responsibilities and interfaces associated with Windows driver development.[5]

Plug and Play allows for detection of devices without user intervention, and occasionally for minor configuration of device resources, such as I/O ports and device memory maps. PnP is a specific set of standards, not be confused with the generic term plug and play, which describes any hardware specification that alleviates the need for user configuration of device resources.[6]

ACPI
is the successor to Legacy Plug and Play.

Overview

The Plug and Play standard requires configuration of devices to be handled by the PnP BIOS, which then provides details of resources allocations to the operating system. The process is invoked at boot time. When the computer is first turned on, compatible devices are identified and assigned non-conflicting

DMA channels
.

The term was adopted by Microsoft in reference to their

Yggdrasil Linux advertised itself as "Plug and Play Linux" at least two years before Windows 95. But the term plug and play
gradually became universal due to worldwide acceptance of Windows.

Typically, non-PnP devices need to be identified in the computer's BIOS setup so that the PnP system will not reassign those devices. Problems in the interactions between legacy non-PnP devices and the PnP system can cause it to fail, leading to this technology having historically been referred to as "plug and pray".[2]

Specifications

Legacy Plug and Play Specification was defined by

PCI and USB
.

  • Plug and Play BIOS Specification[8]
  • Plug and Play ISA Specification[9]
  • Plug and Play Design Specification for IEEE 1394
  • Plug and Play External COM Device Specification[10]
  • Plug and Play Parallel Port Device Specification
  • Plug and Play ATA Specification
  • Plug and Play SCSI Specification
  • Legacy Plug and Play Guidelines

Windows Vista requires an ACPI-compliant BIOS, and the ISAPnP is disabled by default.[11]

Requirements

To use Plug and Play, three requirements have to be met:

  1. The
    OS
    must be compatible with Plug and Play.
  2. The BIOS must support Plug and Play.
  3. The device to be installed must be a Plug and Play compliant device.

Hardware identification

Plug-and-play hardware typically also requires some sort of ID code that it can supply, in order for the computer software to correctly identify it.

This ID code system was not integrated into the early

computer buses like MCA, EISA and PCI
(which was becoming the industry standard at that time) integrated this functionality.

Finally, the operating system of the computer needs to be able to handle these changes. Typically, this means looking for interrupts from the bus saying that the configuration has changed, and then reading the information from the bus to locate what happened. Older bus designs often required the entire system to be read in order to locate these changes, which can be time-consuming for many devices. More modern designs use some sort of system to either reduce or eliminate this "hunt"; for example, USB uses a hub system for this purpose.

When the change is located, the OS then examines the information in the device to figure out what it is. It then has to load up the appropriate device drivers in order to make it work. In the past, this was an all-or-nothing affair, but modern operating systems often include the ability to find the proper driver on the Internet and install it automatically.

See also

References

  1. ^ a b "Final Legacy Plug and Play Paper". Archived from the original on 2016-03-03. Retrieved 2008-10-25.
  2. ^ a b "The PC Guide - Plug and Play (Legacy)". pcguide.com.
  3. ^ tedhudek. "Plug and Play ID - PNPID Request - Windows drivers". docs.microsoft.com. Retrieved 2020-09-09.
  4. ^ "Plug and Play - Architecture and Driver Support". microsoft.com. Microsoft. Archived from the original on 2004-06-16.
  5. ^ "WDM: Introduction to Windows Driver Model". microsoft.com. Microsoft. Archived from the original on 2004-08-29.
  6. ^ "The PC Guide - Plug and Play". pcguide.com.
  7. ^ "DNA/Dongly Things". douglasadams.com.
  8. ^ Compaq; Phoenix Technologies; Intel (May 5, 1994). Plug and Play BIOS Specification (PDF) (Version 1.0A ed.). Archived from the original (PDF) on April 23, 2016. Retrieved June 11, 2015.
  9. ^ Intel; Microsoft (May 5, 1994). Plug and Play ISA Specification (RTF) (Version 1.0A ed.).
  10. ^ Microsoft; Hayes Microcomputer Products. Plug and Play External COM Device Specification (PDF). Archived from the original (PDF) on March 22, 2016.
  11. Microsoft Corporation
    . Retrieved 2010-07-02.

External links