2
Remote Control
2.1 Remote control basis
6
The socket in the signal generator is compatible with Berkeley socket and Winsock through Application
Program Interface (API). In addition, other standard sockets are also compatible through the API. When
the signal generator is controlled using SCPI, the socket program created in the program issues
command. The socket port number of the signal generator must be set before LAN socket is used. For
the signal generator, the socket port number is set to 5,000.
2.1.1.2 GPIB interface
The GPIB interface is a widely-used instrument remote interface currently, which can be connected with
different kinds of instruments through the GPIB cable and can establish the test system with the main
control computer. To realize remote control, the main control computer shall be preinstalled with the
GPIB bus card, driver and VISA library. During communication, the main control computer will address
the controlled instrument through the GPIB bus address firstly. The user can set the GPIB address and
ID for querying strings, and the GPIB communication language can be set to the SCPI form by default.
The operation of the GPIB and its relevant interface is defined and described in details in the ANSI/IEEE
standard 488.1-1987 and the ANSI/IEEE standard 488.2-1992. For details, refer to IEEE website:
http://www.ieee.org
。
As the GPIB processes information in bytes and the data transmission rate can reach 8 MBps, the GPIB
data transmission is faster. The data transmission rate is limited by the distance between the
device/system and the computer. When GPIB is connected, the following points shall be noted:
Up to 15 instruments may be set up through the GPIB interface;
The total length of the transmission cable shall not exceed 15 m, or shall not exceed twice of
number of instruments in the system. The maximum length of transmission cable between
equipment generally does not exceed 2 m.
If you connect multiple instruments in parallel, you need to use ―OR‖ connectors.
The terminal of the IEC bus cable shall be connected with the instrument or the controller
computer.
2.1.2
Message
Messages transmitted by data cable fall into the following two categories:
1) Interface message
During communication between the instrument and the main control computer, it is necessary to pull
down the attention line and then the interface message can be transmitted to the instrument through the
data line. Only the instrument with the GPIB bus functions can send the interface message.
2) Instrument message
For the structure and syntax of instrument message, refer to Section "5.1.4 SCPI". Instrument message
can be divided into command and instrument response according to the different transmission directions.
All remote interfaces use instrument message in the same method unless otherwise stated.
a) Commands:
A command (programming message) is a message transmitted from the main control computer to the
instrument for remote control of instrument functions and query of status information. It falls into the
following two categories:
Based on the impact on the instrument:
— Set command: change the instrument setup status, for example: reset or set the frequency.
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