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 COM_EVENT()
 Designates which event at the port triggered a key trap
------------------------------------------------------------------------------
 Syntax

     COM_EVENT(<nComPort>,<nMode>) --> nCode

 Arguments

     <nComPort>  Designates the port (1 to 4) that is tested for the
     event.

     <nMode>  Designates a numeric value between 1 and 5 (see table 3-2).

 Returns

     This function returns the code of an incoming character, MSR status, LSR
     status, or the number of errors that have occurred to date as a function
     of the <nMode> parameter value.

 Description

     As a rule, it is necessary to determine the cause of a trap if a
     character is placed in the keyboard buffer and the procedure specified
     with SET KEY TO is called.  The numeric parameter determines what
     information is accessed.  The information returned for modes 1 to 5 are
     defined as follows:

     Table 3-2: Query Codes for Event Information
     ------------------------------------------------------------------------
     Code    Event Information
     ------------------------------------------------------------------------
     1       The function will return the ASCII code of the incoming
             character.  If no character is available, a -1 is returned.
     2       The function returns the status of the MS register at the time
             of the interrupt.
     3       The function returns the status of the LS register at the time
             of the interrupt.
     4       The value of the internal error counter will be returned. The
             error events in the LSR since the last COM_INIT() will be
             counted.
     5       Returns the number of characters which had to be rejected
             because the buffer was 100% full.
     ------------------------------------------------------------------------

 Notes

     .  With the exception of the error counter, all status
        information is reset when you open the port or when you call
        COM_KEY() again.

     .  The conditions of MSR and LSR are considered at each interrupt
        and are linked to the respective status byte in the internal
        environment through a logical OR operation.  It is therefore possible
        to place multiple bits in one of the registers.

     .  Overrun errors, parity errors, and frame errors (bits 1 to 3)
        are counted as errors exclusively.

     Important!  The input lines on conventional PC interface cards are
     normally not terminated.  This can lead to inexplicable results when you
     query the MSR.

 Example

     Determine the number of errors that have occurred:

     nErrorCnt  :=  COM_EVENT(1, 4)

     IF nErrorCnt > 25
        * more than 25 errors?
        ? "Too many errors -  terminate program!"
        lRelease  :=  .T.
     ENDIF