B&K Precision 4079 - Manual - Manual (Page 43)

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Section 4
Programming
4.1 Overview
4.1.1 GPIB
This section provides detailed information on programming the 4076 and 4079 via the IEEE 488 bus (referred to from now as
the GPIB - General Purpose Interface Bus). The 4076 and 4079 are programmable over the IEEE 488.1 bus, and its message
protocol is compatible with IEEE 488.2. The device command set is compatible with the SCPI 1992.0 standard.
The command syntax as defined by the IEEE 488.2 and SCPI standards is briefly explained in the following sections. Users
who have experience programming GPIB instruments may skip these paragraphs, and go directly to where the individual
command syntax is given in sections 4.12 and 4.13. Considering the relative newness of these standards, it is recommended
to all users to read the explanations given here. Users wishing to gain further insight should consult the standards.
4.1.2 RS-232-C
The INSTALLATION section of this manual describes the RS-232-C connection for the instrument. Be sure that
you have the Remote Mode set to RS-232 and correctly set the baud rate.
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. The instrument can be set to
different baud rates ranging from 1200 to 115,000 as described in Section 3, Operating Instructions.
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. Refer to section 2.9 .
The serial interface implements the same SCPI command set as the GPIB interface. This includes commands stated in
sections 4.12 and 4.13. Refer to these sections for syntax details. 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 receive via RS232 will change the display screen with the following: