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Opens and initializes a communications channel for input or output (I/O).
The OPEN COM statement must be executed before a device can be used for
communication using an RS232 interface.
 
OPEN "COMn: optlist1 optlist2" [FOR mode] AS [#]filenum% [LEN=reclen%]
 
    ■ n           The communications port to open (1 = COM1, 2 = COM2).
    ■ optlist1    The most-often-used communications parameters:
                    [baud] [,[parity] [,[data] [,[stop]]]]
                  baud is the baud rate of the device to be opened:
                    75, 110, 150, 300, 600, 1200, 2400, 4800, 9600
                  parity is the method of parity checking:
                    N (none)     E (even)    O (odd)
                    S (space)    M (mark)    PE (enable error checking)
                  data is the number of data bits per byte:
                    5, 6, 7, 8
                  stop is the number of stop bits:
                    1, 1.5, 2
                  Defaults: 300 baud, even parity, 7 data bits, 1 stop bit.
    ■ optlist2    A list of less-often-used parameters, separated by commas:
 
                  Option    Description
                  ══════    ══════════════════════════════════════════════════
                  ASC       Opens the device in ASCII mode.
                  BIN       Opens the device in binary mode.
                  CD[m]     Sets the timeout period (in milliseconds) on the
                            Data Carrier Detect (DCD) line.
                  CS[m]     Sets the timeout period (in milliseconds) on the
                            Clear to Send (CTS) line.
                  DS[m]     Sets the timeout period (in milliseconds) on the
                            Data Set Ready (DS) line.
                  LF        Sends a line-feed character after a carriage
                            return.
                  OP[m]     Specifies how long (in milliseconds) OPEN COM
                            waits for all communications lines to become open.
                  RB[n]     Sets the size (in bytes) of the receive buffer.
                  RS        Suppresses detection of Request to Send (RTS).
                  TB[n]     Sets the size (in bytes) of the transmit buffer.
 
    ■ mode        INPUT, OUTPUT, or RANDOM (the default).
                  See ◄OPEN Statement File Modes►.
    ■ filenum%    A number in the range 1 through 255 that identifies the
                  communications channel as long as it is open.
    ■ reclen%     Random-access-mode buffer size (default is 128 bytes).
 
Example:
    'Use this example for trouble shooting serial communications problems.
    'Slow baud, hardware handshaking is ignored and buffers are enlarged.
    OPEN "COM1:300,N,8,1,CD0,CS0,DS0,OP0,RS,TB2048,RB2048" FOR RANDOM AS #1
 
See Also    ◄OPEN►