0040h:007Ch           Time-Out Values for RS-232 Communications Lines

    Length: 4 bytes

    These bytes are used to test when the RS-232 Communications lines
    will time-out.

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    These bytes are used to test when the RS-232 Communications lines
    will time-out. These values are usually 01h. On the PC and XT,
    these values tend to represent the number of seconds before a
    time-out. On other machines, such as the AT, these values are
    still 01h, but in the time- out test, these values are multiplied
    by 4 to compensate for the increased speed of the AT. However, the
    actual number of seconds before a time-out situation is about
    twice the time-out values stored here. In any case, these values
    should NOT be looked on as the number of seconds before a
    time-out, but instead should represent the amount of time needed
    to detect a time-out situation.

        0040h:007Ch - Serial Port #1 Time-out Value (COM1)
        0040h:007Dh - Serial Port #2 Time-out Value (COM2)
        0040h:007Eh - Serial Port #3 Time-out Value (COM3)
        0040h:007Fh - Serial Port #4 Time-out Value (COM4)