DLS DLS 400A, Operating Manual

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REMOTE CONTROL
Page 60
7.2 RS–232 Serial Interface
The DLS 400 uses a female DB–25 connector, and is configured as a DCE device.
The RS–232 standard is equivalent to the European V.24/V.28 standards. In this manual
we use the term RS–232 to refer to both of these two standards. Generally, the computer
literature will use the words “serial”, “COM1” and “COM2” to refer to the RS–232 inter-
face. Note that the DLS 400 cannot use the parallel port of a computer.
To use the RS–232 interface, simply connect your computer to the DLS 400 and set the
computer to 9600 bps baud rate, no parity, 8 data bits per character, and 1 stop bit.
Do NOT use a null modem with a computer that has a standard COM port configured as a
DTE.
The DLS 400 stops transmitting data when the RTS line is low, and restarts when the RTS
line is high. The DLS 400 lowers the CTS and the DSR lines when it cannot accept data,
and raises them when it can. Note that the RTS line is not the usual “Request To Send” as
defined by the RS–232 standard. If desired, the user can leave the RTS line set, and use
only the CTS line.
7.2.1 Message Terminators
Messages sent to the DLS 400 through the serial interface MUST be terminated with the
line feed character (decimal 10, hex 0A, LF). To ensure that no characters are left in the
receive buffer of the DLS 400 from a previous incomplete command, you can send the
line feed character by itself before sending new commands.
Messages from the DLS 400 are always terminated with a Line Feed character.
Note that some languages, such as BASIC, may automatically append a carriage return
and a line feed at the end of messages. The carriage return character is not a valid termina-
tor, and will invalidate the last command. To avoid this problem, you can append a semi-
colon after a string (after the quotes) when printing to the IEEE 488 port. Another solution
is to append a semi-colon at the end of the command itself (inside the quotes), so that the
carriage return can be interpreted as a second command, and be simply discarded by the
DLS 400. For example:
PRINT #1,”:set:channel:length 1000”+CHR$(10); Preferred solution
or
PRINT #1,”:set:channel:length 1000;” Alternate solution