Stanford Research Systems SR830, Manual

Page: 84 / 177

completed.
To help find program errors, the SR830 can dis-
play its receive buffer on the displays. Use the
[Setup] key to access the QUEUE display. The
last 256 characters received by the SR830 may be
displayed in hexadecimal ASCII. See the
OPERATION section for a complete description.
COMMAND SYNTAX
Communications with the SR830 uses ASCII char-
acters. Commands may be in either UPPER or
lower case and may contain any number of
embedded space characters. A command to the
SR830 consists of a four character command
mnemonic, arguments if necessary, and a com-
mand terminator. The terminator must be a line-
feed <lf> or carriage return <cr> on RS232, or a
linefeed <lf> or EOI on GPIB. No command pro-
cessing occurs until a command terminator is
received. Commands function identically on GPIB
and RS232 whenever possible. Command mne-
monics beginning with an asterisk "
❊
" are IEEE-
488.2 (1987) defined common commands. These
commands also function identically on RS232.
Commands may require one or more parameters.
Multiple parameters are separated by commas (,).
Multiple commands may be sent on one command
line by separating them with semicolons (;). The
difference between sending several commands on
the same line and sending several independent
commands is that when a command line is parsed
and executed, the entire line is executed before
any other device action proceeds.
There is no need to wait between commands. The
SR830 has a 256 character input buffer and pro-
cesses commands in the order received. If the
buffer fills up, the SR830 will hold off handshaking
on the GPIB and attempt to hold off handshaking
on RS232. Similarly, the SR830 has a 256 charac-
ter output buffer to store outputs until the host
computer is ready to receive. If either buffer over-
flows, both buffers are cleared and an error
reported.
The present value of a particular parameter may
INTRODUCTION
The SR830 DSP Lock-in Amplifier may be remote-
ly programmed via either the RS232 or GPIB
(IEEE-488) interfaces. Any computer supporting
one of these interfaces may be used to program
the SR830. Both interfaces are receiving at all
times, however, the SR830 will send responses
to only one interface. Specify the output inter-
face with the [Setup] key or use the OUTX com-
mand at the beginning of every program to
direct the responses to the correct interface.
COMMUNICATING WITH GPIB
The SR830 supports the IEEE-488.1 (1978) inter-
face standard. It also supports the required
common commands of the IEEE-488.2 (1987)
standard. Before attempting to communicate with
the SR830 over the GPIB interface, the SR830's
device address must be set. The address is set
with the [Setup] key and may be set between 1
and 30.
COMMUNICATING WITH RS232
The SR830 is configured as a DCE ( transmit on
pin 3, receive on pin 2) device and supports CTS/
DTR hardware handshaking. The CTS signal (pin
5) is an output indicating that the SR830 is ready,
while the DTR signal (pin 20) is an input that is
used to control the SR830's data transmission. If
desired, the handshake pins may be ignored and a
simple 3 wire interface (pins 2,3 and 7) may be
used. The RS232 interface baud rate and parity
must be set. These are set with the [Setup] key.
The RS232 word length is always 8 bits.
STATUS INDICATORS AND QUEUES
To assist in programming, the SR830 has 4 inter-
face status indicators. The ACTIVE indicator flash-
es whenever a character is received or transmitted
over either interface. The ERROR indicator flash-
es when an error, such as an illegal command, or
parameter out of range, has been detected. The
REMOTE indicator is on whenever the SR830 is in
a remote state (front panel locked out). The SRQ
indicator is on when the SR830 generates a ser-
vice request. SRQ stays on until a serial poll is
REMOTE PROGRAMMING
5-1