Resumo de I/o Port - andrew taunenbaum

USB:

-Short for Universal Serial Bus

- an external bus standard that supports data transfer rates of 12 Mbps.

-A single USB port can be used to connect up to 127 peripheral devices, such as mice, modems, and keyboards.

- USB also supports Plug-and-Play installation and hot plugging.
- It is expected to completely replace serial and parallel ports.
- The maximum cable length is 5 meters, or about 16 feet. Since each hub is a repeater, the signal can be propagated through additional cables for up to six total hubs, that is, five connecting cables of up to 15 feet each with the final upstream and down-stream hubs at each end.

IEEE 1394:

FIRE WIRE

-A very fast external bus standard that supports data transfer rates of up to 400Mbps (in 1394a) and 800Mbps (in 1394b).

- Products supporting the 1394 standard go under different names, depending on the company.

-Apple, which originally developed the technology, uses the trademarked name FireWire. Other companies use other names, such as i.link and Lynx, to describe their 1394 products.
-A single 1394 port can be used to connect up 63 external devices.
-In addition to its high speed, 1394 also supports isochronous data -- delivering data at a guaranteed rate. This makes it ideal for devices that need to transfer high levels of data in real-time, such as video devices.
-Although extremely fast and flexible, 1394 is also expensive.
-Like USB, 1394 supports both Plug-and-Play and hot plugging, and also provides power to peripheral devices
-Cable Limitation: 4.5 meters with standard cables, 10 meters with Granite Digital cables.

Serial port:

-A port, or interface, that can be used for serial communication, in which only 1 bit is transmitted at a time.
-Most serial ports on personal computers conform to the RS-232C or RS-422 standards.
- A serial port is a general-purpose interface that can be used for almost any type of device, including modems, mice.
RS232 cable length according to Texas Instruments
Baud rate
Maximum cable length (ft)
19200
50
9600
500
4800
1000
2400
3000

Parallel port:

-A parallel interface for connecting an external device such as a printer.

- Most personal computers have both a parallel port and at least one serial port.
-On PCs, the parallel port uses a 25-pin connector (type DB-25) and is used to connect printers, computers and other devices that need relatively high bandwidth.
- It is often called a Centronics interface after the company that designed the original standard for parallel communication between a computer and printer. (The modern parallel interface is based on a design by Epson.)
-A newer type of parallel port, which supports the same connectors as the Centronics interface, is the EPP (Enhanced Parallel Port) or ECP (Extended Capabilities Port). Both of these parallel ports support bi-directional communication and transfer rates ten times as fast as the Centronics port.
-The maximum cable length of the parallel port is approximately 50 ft.

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