GW Instek GDS-2000 series Programming manual - Manual (Page 18)

GDS-2000 Series Programming Manual
18
As shown in the figure 3-1, the IEEE-488.1 standard locates at layer A, the layer A
is belonged to the protocol of interface function on the GPIB bus. The source
handshake (SH), acceptor handshake (AH) and talker are included in this layer (10
interface functions totally).
At layer B, the syntax and data structure could be the essence of entire IEEE-488.2
standard. The syntax defines the function of message communication, which
contain the (or simply “commands”) and
MESSAGE>. The two kinds of messages are represented the syntax formation of
device command and return value. The data structure is the constitution of status
reporting, which IEEE-488.2 standard have been defined.
The common commands and queries are included with layer C. Commands and
queries can be divided into two parts: mandatory and optional. Commands modify
control settings or tell the instrument to perform a specific action. Queries cause the
instrument to send data or status information back to the computer. A question
mark at the end of a command identifies it as a query.
Layer D is interrelated with device information. Different devices have different
functions. SCPI command sets are belonged to this layer.
Command Syntax
If you want to transfer any of the instructions to an instrument, and comply with
SCPI, there are three basic elements must be included.
z
Command header
z
Parameter (if required)
z
Message terminator or separator