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Using the External UART

The MCBx51 includes an external 16550 UART.

The I/O library (\KEIL\C251\EXAMPLES\MCB251\MCB251C2.LIB) contains routines to transmit and receive serial data using the external UART. The \KEIL\C251\EXAMPLES\MCB251\MCB251C2.UV2 project builds the MCB251C2 library. The ABSTRACT.TXT file in this project folder contains an overview of the functions available.

The library for the MCBx51 board may be used with the Intel 251Sx/Tx and Atmel AT/TSC80251G1D/G2D devices (in Source Mode). You may add the library to your projects to communicate using the EXT RS232 UART of the MCBx51 board. The Hello and Measure example programs in the \KEIL\C251\EXAMPLES\ folder use this library.

You may replace the default run-time library _getkey and putchar routines with those from the MCB251C2.LIB.

  1. Add the library to your project.
  2. In the Project Window, right-click on the library and select Options for File.

    Options dialog

  3. In the Options Dialog, under Select Modules to Always Include, make certain that the GETKEY and PUTCHAR modules are selected. These object modules contain the _getkey and putchar functions.

    Library Options dialog

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