Stanford Research Systems SR620, Руководство пользователя

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30 Programming Commands
SR620 Universal Time Interval Counter
synchronization to be achieved using the
synchronization commands.
There is no need to wait between commands. The
SR620 has a 256 character input buffer and
processes commands in the order received. If the
buffer fills up the SR620 will hold off handshaking
on the GPIB and attempt to hold off handshaking
on RS232. If the buffer overflows the buffer will be
cleared and an error reported. Similarly, the
SR620 has a 256 character output buffer to store
output until the host computer is ready to receive
it. If the output buffer fills up it is cleared and an
error reported. The GPIB output buffer may be
cleared by using the Device Clear universal
command.
The present value of a particular parameter may
be determined by querying the SR620 for its
value. A query is formed by appending a question
mark "?" to the command mnemonic and omitting
the desired parameter from the command. If
multiple queries are sent on one command line
(separated by semicolons, of course) the answers
will be returned in a single response line with the
individual responses separated by semicolons.
The default response terminator that the SR620
sends with any answer to a query is carriage
return-linefeed <cr><lf> on RS232 and linefeed
plus EOI on GPIB. The RS232 terminator may be
changed using the ENDT command, while the
GPIB terminator is fixed. All commands return
integer results except as noted in individual
command descriptions.
Examples of Command Formats
TERM
1, 1 <lf> Sets the A channel input
impedence to 1 Mohm (2
parameters).
TERM? 1 <lf> Queries the A input
termination (query of 2
parameter command).
.*IDN? <lf> Queries the device
identification (query, no
parameters).
STRT <lf> Starts a measurement no
parameters).
MODE 1 ; MODE? <lf>
Sets mode to width (1) then
queries the mode.
Detailed Command List
The four letter mnemonic in each command
sequence specifies the command. The rest of the
sequence consists of parameters. Multiple
parameters are separated by commas.
Parameters shown in {} are optional or may be
queried while those not in {} are required.
Commands that may be queried have a question
mark? in parentheses (?) after the mnemonic.
Commands that may ONLY be queried have a ?
after the mnemonic. Commands that MAY NOT
be queried have no?. Do not send ( ) or { } as part
of the command.
Variable i is an integer that selects an input
channel for the command:
i Channel
0 External input
1 A input
2 B input
The variables j,k,l,m, and n are also integers. The
variable x is a real number.
All variables may be expressed in integer, floating
point or exponential formats ( ie., the number five
can be either 5, 5.0, or .5E1).
IMPORTANT NOTE: ALL of the front panel
settings to the left of the "CONFIG" button, and the
JITTER type (Allan variance or standard deviation)
are properties of the present operating mode and
are saved when the mode is changed. Thus, if the
mode is changed the previous settings of these
parameters in the new mode will automatically be
set. The programmer MUST be careful to set all
relevant parameters each time the mode is
changed to prevent conflicts between the
presumed and actual states of the instrument.
Trigger Control Commands
LEVL(?) i {,x}
The LEVL command sets, or reads, the trigger
threshold for channel i. If the SR620 is in the
autolevel mode, this command will turn off the
autolevel mode and set the desired threshold.
The trigger level set by the LEVL command will
remain in effect until the front panel knob is
rotated. In remote mode the front panel knob is
ignored. If the trigger level is queried (LEVL? i )
the answer returned is a floating point number with
2 digits to the right of the decimal point, for
example, -1.07.