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COM port overrun error

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  • COM port overrun error

    I am testing a quad serial card (connects via PCI) and the ports keep failing BIT 6.0 for an overrun error. I was wondering if anyone has noticed communications ports failing due to an LPT port being present or if anyone else has run into issues with a PCI serial card failing?

  • #2
    This warning can be related to load on the COM port and the CPUs ability to service the COM port interrupts (ie. CPU load and interrupt priorities).

    You could try changing:
    (1) reduce the CPU load by reducing the number of tests (including the CPU and memory tests);
    (2) the COM port speed (reduce);
    (3) the COM port duty cycle (reduce);
    (4) the UART settings (please see: ). For example reduce both buffers to 8 (ensure that the transmit FIFO is not larger than the receive FIFO).
    (5) If you are also running the optical disk test at the same time, then you could also check that the CD/DVD drive is on a controller that is set to DMA rather than PIO .