Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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     IRQ4 remains inactive until bit 4 is cleared in the interrupt
     controller's mask register.
 
     To access data from the COM1 port directly, a program must set up
     a handler routine to read the port when the interrupt occurs. It
     must also program the Universal Asynchronous Receiver/Transmitter
     (UART).
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