DTR / DSR Handshake Protocol
The function generator is configured as a DTE (Data Terminal Equipment)
device and uses the
DTR (Data Terminal Ready) and DSR (Data Set Ready)
lines of the
RS-232 interface to handshake. The function generator uses
the
DTR line to send a hold-off signal. The DTR line must be TRUE
before the function generator will accept data from the interface. When
the function generator sets the
DTR line FALSE, the data must cease
within 10 characters.
To disable the
DTR/DSR handshake, do not connect the DTR line and tie
the
DSR line to logic TRUE. If you disable the DTR/DSR handshake, also
select a slower baud rate (300, 600, or 1200 baud) to ensure that the
data is transmitted correctly.
The function generator sets the DTR line FALSE in the following cases:
1 When the function generator’s input buffer is full (when approximately
100 characters have been received), it sets the
DTR line FALSE (pin 4 on
the
RS-232 connector). When enough characters have been removed to
make space in the input buffer, the function generator sets the
DTR line
TRUE, unless the second case (see below) prevents this.
2 When the function generator wants to “talk” over the interface (which
means that it has processed a query) and has received a <new line>
message terminator, it will set the
DTR line FALSE. This implies that
once a query has been sent to the function generator, the controller
should read the response before attempting to send more data. It also
means that a <new line> must terminate the command string. After the
response has been output, the function generator sets the
DTR line
TRUE again, unless the first case (see above) prevents this.
The function generator monitors the
DSR line to determine when the
controller is ready to accept data over the interface. The function
generator monitors the
DSR line (pin 6 on the RS-232 connector) before
each character is sent. The output is suspended if the
DSR line is
FALSE. When the DSR line goes TRUE, transmission will resume.
Chapter 4 Remote Interface Reference
RS-232 Interface Configuration
198
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