B&K Precision 4034 - Manual - Manual (Page 36)

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EIA standard RS-232-C specifies the electrical characteristics and pin out of a serial communication standard for
connecting "data terminal equipment" (DTE) to "data communication equipment" (DCE). Data terminal equipment
is usually devices such as terminals, computers, or printers that are the final destination for data. Data
communication equipment, on the other hand, is usually a modem or other device that converts the data to another
form and passes it through. The instrument can be configured only as a DCE, so in most cases it can be connected
with a straight-through cable to a computer, but would require special cabling to connect to another DCE device.
The baud rate is the bit rate during the transmission of a word in bits per second. Different devices use many baud
rates, but the baud rates of the two devices that are connected must be the same.
Data signals over the RS-232-C use a voltage of +3V to +25V to represent a zero (called a space) and a voltage of -
3V to -25V to represent a one (called a mark). Handshake and control lines use +3V to +25V to indicate a true
condition and -3V to -25V to indicate a false condition.
When no data is being transmitted, the idle state of the data lines will be the mark state. To transmit a byte, the
transmitting device first sends a start bit to synchronize the receiver.
The RS-232-C standard is not very specific about many of the handshaking signals and it is therefore usually
necessary to refer to the manuals for both of the devices being connected to determine the exact pin out, signal
definition, and signal direction for the devices.
The serial interface implements the same SCPI command set as the GPIB interface. The instrument is
programmed by sending ASCII coded characters to the instrument.
When the instrument is in the remote mode, remote command input has priority over any front panel control.
Therefore, as long as the serial interface is continuously supplied with data, the keyboard will appear to be
inoperative to the user.
Note: In remote mode, any command sent or received via RS232 will change the display screen with the
following:
User can return to local control with the press of any front panel keys, but it is extremely important to note that
this should be done ONLY
when nothing is being sent or transferred between the instrument and the connected
PC. Any interruptions during transfer may delay the communication process or cause communication errors.
The instrument accepts a line feed (LF) as an end of string (EOS) terminator.
4.2 Device State
The device may be in one of the four possible states described below. The transition between states is defined by
IEEE 488.1.
4.2.1 Local State (LOCS)