what is a uart and how do I identify it on mobo

Posted on 2011-10-28
Last Modified: 2012-05-12
what is a uart and how do I identify it on mobo
Question by:now2010
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    It is the chip for serial rs 232 type interfaces. Often it is a 16550, 8250, gd75232d chip etc. Normally the chip will be close to the actual ports, so look at those chips more closely.
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    UARTs (Universal Asynchronous Receiver Transmitter) are serial chips on your PC motherboard (or on an internal modem card). The UART function may also be done on a chip that does other things as well. On older computers like many 486's, the chips were on the disk IO controller card. Still older computer have dedicated serial boards.

    The UART's purpose is to convert bytes from the PC's parallel bus to a serial bit-stream. The cable going out of the serial port is serial and has only one wire for each direction of flow. The serial port sends out a stream of bits, one bit at a time. Conversely, the bit stream that enters the serial port via the external cable is converted to parallel bytes that the computer can understand. UARTs deal with data in byte-sized pieces, which is conveniently also the size of ASCII characters.

    As for locating it on the motherboard generally the UART is going to be a long thin chip.although sometimes it is a square chip. Like Rindi said it will most likely be in the proximity of the the serial port

    Say you have a terminal hooked up to your PC. When you type a character, the terminal gives that character to its transmitter (also a UART). The transmitter sends that byte out onto the serial line, one bit at a time, at a specific rate. On the PC end, the receiving UART takes all the bits and rebuilds the (parallel) byte and puts it in a buffer.

    Along with converting between serial and parallel, the UART does some other things as a byproduct (side effect) of its primary task. The voltage used to represent bits is also converted (changed). Extra bits (called start and stop bits) are added to each byte before it is transmitted. Voltage Wave shapes'' for details. Also, while the flow rate (in bytes/sec) on the parallel bus inside the computer is very high, the flow rate out the UART on the serial port side of it is much lower. The UART has a fixed set of rates (speeds), which it can use, at its serial port interface.

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    Sorry for the delay, thank you.

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