- 8250
reference frequency.
The chip designations carry suffix letters for later versions of the same chip series. For example, the original 8250 was soon followed by the 8250A and 8250B versions that corrected some bugs.
Due to the high demand, other manufacturers soon began offering compatible chips.
Western Digital offered WD8250 chip under Async Communications Interface Adapter (ACIA) and Async Communications Element (ACE) names.The 16450(A) UART, commonly used in
IBM PC AT -series computers, improved on the 8250 by permitting higher serial line speeds.With the introduction of
multitasking operating systems on PC hardware, such asOS/2 ,Windows NT or various flavours ofUNIX , the short time available to serve character-by-characterinterrupt requests became a problem, therefore later serial ports used the 16550(A) UARTS that had a built-in 16 byteFIFO or buffer memory to collect incoming characters.Later models added larger memories, supported higher speeds, combined multiple ports on one chip and finally became part of the now-common
Super I/O circuits combining most input/output logic on a PCmotherboard .External links
* [http://www.lammertbies.nl/comm/info/serial-uart.html Serial UART, an in-depth tutorial]
* [http://www.freebsd.org/doc/en_US.ISO8859-1/articles/serial-uart/index.html Serial and UART Tutorial]
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