Tandy 1000 Basic Reference Manual page 247

Chapter 10 I BASIC Keywords
Buffer is a number in the range 1 to 15, indicating the buffer
that accesses the file. The number sign
(#)
is optional. It is pro-
vided for compatibility with other BASICs.
Number specifies the maximum number of bytes that can be ac-
cessed in the communications buffer by GET and PUT state-
ments. If you omit the
LEN option, BASIC assumes 128 bytes.
The parameters speed, parity, data, and stop are all positional.
That is, they must be in the order specified in the syntax. If you
omit one of the parameters, you must still include the comma to
hold its position.
The remaining parmeters are not positional. They may be in any
order, or you may omit them. They control the software commu-
nication signal lines between 2 terminals. If you omit the CS,
DS, or CD options, the signals are not checked a t all. Include
them only if you are testing these software signals.
The RS option suppresses the Request To Send (RTS) signal. Re-
quest To Send is a signal that is sent from the sending terminal
to the receiving terminal to ensure that the receiving terminal
is ready to accept communication data. When you execute an
OPEN COM statement, the RTS line is turned on, unless you in-
clude the RS option.
The CS option controls the Clear To Send (CTS) signal which is
sent from the receiving terminal to the sending terminal to let
the sending terminal know that the receiving terminal is ready
to receive.
You can think of RTS and CTS as a hand-shaking exercise, in
which the 2 terminals let each other know that they are ready to
send and/or receive data. RTS is an output signal from the send-
ing terminal, and
CS
is an input signal to the sending terminal.
The DS option controls the Data Set Ready
(DSR)
signal. The
DSR signal ensures that a data set, such as a modem, is present
to transmit the data.
The CD option controls the Carrier Detect (CD) signal. The CD
signal is an input signal which ensures that the data set is
ready to transmit the data.
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