USB ports - (Universal Serial Bus) are high-speed serial-bus architecture designed for desktops and portable computers.
USB SYMBOL
These high-speed communication ports greatly out-perform the standard serial and parallel ports and are alternatives for SCSI (Small Computer Serial Interface) peripheral connections.
Because of their design, they make installation and configuration of Input/Output (I/O) devices easy, providing room for as many as 127 devices daisy-chained together.
It must not be assumed that if a PC has 2 USB ports, you could connect 254 devices. (127 x 2). This is not possible since each USB controller can only support a maximum of 127 devices. To install more than the maximum, you will have to install additional USB ports and bus controller hardware via the use of adapter cards.
USB signals normally travel approximately 16 feet before they begin to degrade.
USB is an external bus standard designed for enhancing plug and play capabilities for attaching peripherals to your PC.
A very important feature of this bus is the elimination of the need for special-purpose ports and special-purpose I/O cards.
USB ports also save important system resources such as interrupts (IRQs) and, regardless of the number of devices attached to them, only one IRQ is required.
Intel first introduced the USB architecture and all its motherboard chipsets since the PIIX3 South Bridge chipset (February 1996) have USB as a standard feature.
Other chipset manufacturers have also followed and made USB ports a standard feature of today's PCs - just like the serial and parallel ports.
The USB 1.0 standard was released in January 1996, followed by USB 1.1 in September 1998. It was designed to run at 12Mbit/sec (1.5MB/sec) over a four-wire connection.
The USB 1.1 was upgraded to USB 2.0 which ran 40 times faster and was fully backward compatible.
Older computers without built-in USB ports can be upgraded by installing an add-on PCI card (desktop computers) or a PC card on a Cardbus-compatible laptop computer.
Connectors
There are two distinct types of USB connectors; namely Series A and Series B. The Series A connector is made for devices in which the cable remains permanently attached such as hubs, keyboards, mice, etc. Series B connectors are made for devices that require detachable cables such as printers, scanners, modems, telephones, speakers, etc.
| | |
| Series A | Series B |
Diagram of Series A and B Male USB Connectors
Unlike serial or parallel connectors, USB connectors are small and the plug is not attached by screws. This makes USB devices very easy to install and uninstall.
Final Thoughts
USB ports are a standard on virtually all PCs today and is used for general purpose external high-speed interfacing.
If your present system does not have any of these ports, you can install a USB card in a PCI slot on your motherboard.
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