UART

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UART

[′yü‚ärt]
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

UART

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UART

(Universal Asynchronous Receiver Transmitter) The electronic circuit that makes up the serial port. Also known as "universal serial asynchronous receiver transmitter" (USART), it converts parallel bytes from the CPU into serial bits for transmission, and vice versa. It generates and strips the start and stop bits appended to each character. Note that in the following paragraphs, dashes have been added after the 16 for readability. Older 8250 and 16-450 UARTs are not fast enough for today's modems. A 16-550 is required for transmission up to 115,200 bps (115 Kbps).

ISDN users running both 64 Kbps channels are losing performance with a 16-550 UART, because the maximum 115 Kbps is reduced further to 92 Kbps when the start/stop bits are removed. Upgrading to a 16-650 or higher UART boosts real data speed from 92 to 128 Kbps. The 16-650 is the more sophisticated UART, providing hardware flow control that reduces the burden on the CPU. See UART overrun.

 Buffer    MaximumUART    Size      SpeedChip    (bytes)   Bits/sec
   8250     None        9,600
   16450       1        9,600
   16550      16      115,200
   16650      32      430,800
   16750      64      921,600
   16850     128          1.5 Mbps
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
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Additional key features of the PIC18F4523 microcontroller family include 10 MIPS performance, 32 or 16 Kbytes of enhanced Flash program memory, 256 bytes of EEP-ROM data memory, up to 1,536 bytes of RAM, two analog comparators with input multiplexing, up to two capture/compare/PWM modules, a master 12C and SPI communication module, enhanced USART module with RS485, RS232 and LIN support, one 8-bit and 3x 16-bit timers, and an internal oscillator (32 MHz to 31 kHz.)
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