ENVS 1200 Lecture 2: ENVS 1200 Lecture 2 Notes
13 May 2018
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ENVS 1200 Lecture 2 Notes – Physically Mounted
Introduction
• Devices that are physically mounted within the system are generally connected to I/O
device controllers that are either plugged into a system bus connector on a
motherboard or permanently wired to the bus.
• Buses and network connections also provide a means for devices external to the system
buses to communicate with the system.
• Such I/O devices are commonly called peripherals or peripheral devices because they
are connected peripherally to the system.
• Keyboards, mice, printers, and many other devices are often designed to operate from a
standard port.
• A reminder: a port is simply a connector at the end of a bus into which a device can be
plugged.
• General control for the port is provided by a port controller.
• The port controller connects to a standard bus, such as a PCI or ISA bus.
• Specific device control is built into a controller within some devices and into the
computer software programs that control I/O from these devices.
• These programs are called device drivers.
• Device drivers are either built into the oputer’s operatig syste.
• They are installed into the operating system as supplements to the system.
• Other devices are controlled by controllers and device drivers associated with the
particular bus port.
• In this case, the controllers also convert the bus signals between the form that is used
on the main bus and the form required at the port where the alternative bus is to be
connected.
• Until recently, most printers, modems, and mice were connected to computer systems
through general I/O bus ports called parallel and serial ports.
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