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Programming Command Types and Format
The 575 Pulse Generator uses two types of programming commands: IEEE
488.2 Common Commands and Standard Commands for Programmable
Instruments (SCPI). The format is the same for all interfaces. HyperTerminal (in
Windows) or any other generic terminal program may be used to interactively test
the commands using the RS232 interface. The format of each type is described
in the following paragraphs.
Line Termination
The pulse generator uses text-style line terminations. When a command is sent
to the unit, the firmware is programmed to read characters from a communication
port until it reads the line termination sequence.
The command string is parsed and executed after reading these characters.
These characters are the “carriage return” and “linefeed”. They are ASCII
char-acter set values 13 and 10 respectively (hex 0x0D and 0x0A). All command
strings need to have these characters appended.
When the pulse generator responds to a command, whether it is a query or a
parameter change, it also appends its return strings with these characters.
Coded applications could use this behavior to know when to stop reading from
the unit. However, if the “echo” parameter is enabled, there will be two sets of
line terminators, one following the echoed command string, and one following the
pulse generator’s response.
Note: The pulse generator will echo commands on the DB9 serial port only.
The pulse generator responds to every communication string. If the
communica-tion string is a query, the unit responds with the queried response (or
error code) followed by the line terminators. If the communication string is a
parameter change, the response is “ok” (or error code) followed by the line
terminators. For this reason, it is not recommended that multiple commands be
stacked together into single strings as is common with some other types of
instruments. It is recommended that the coded application send a single
command in a string and follow immediately by reading the response from the
unit. Repeat this sequence for multiple commands.
IEEE 488.2 Common Command Format
The IEEE 488.2 Common Commands control and manage generic system
functions such as reset, configuration storage and identification. Common
commands always begin with the asterisk (*) character and may include
param-eters. The parameters are separated from the command pneumonic by a
space character. For Example:
*RST<cr><lf>
*RCL 1<cr><lf>