Data Communications Equipment; Wait Command; Termination Sequence; Gpib (Ieee-488) Interface - Stanford Research Systems SR510 Manual

Data Communications Equipment

(DCE)
The SR510 is configured as DCE so that it may be
connected directly to a terminal. If the SR510 is to
be interfaced with another DCE device, a special
cable (sometimes referred to as a 'modem' cable)
is required. To use the RS232 interface you must
set the switches in SW2 to match your computer's
baud rate, parity, and number of stop bits. Refer
to Page 7 for details.

Wait Command

The SR510 normally waits until the RS232 'Clear
to Send' control line (CTS) is asserted before
sending characters. However, some computers
do not set and reset the CTS line, possibly
causing the SR510 to send data when the
computer is not ready to read it. The SR510 may
be 'slowed down' using the W command. Sending
'Wn' causes the unit to wait nX4 mS before
sending each character over the RS232 bus. The
command W0 sets the wait interval to zero and
results in the fastest transmission. The wait
interval is set to 6 (24 mS) on power-up.
Termination Sequences
The default RS232 termination characters are
sufficient to interface with most computers,
however, it will occasionally be necessary to send
special terminating sequences to fit the
requirements of some computers. This can be
done with the J command. The format for the
command is:
J {n1,n2,n3,n4}
where n1, n2, n3, and n4 are decimal values
between 0 and 255 corresponding to the decimal
ASCII codes of the desired termination characters.
For instance, if the desired termination sequence
is an asterisk, (ASCII 42), two carriage returns,
(ASCII 13), and a line feed, (ASCII 10), the
appropriate command is:
J 42,13,13,10
If a G command is sent requiring an answer of 24
(sensitivity = 500 mV), the SR510 would respond
with the string
24*<cr><cr><lf>
Up to four terminating characters may be specified
by the J command. If no arguments are sent with
the J command, the terminating sequence returns
to the default (echo on: <cr><lf>; echo off: <cr>).
The J command does not affect the terminating
character (<cr>) required at the end of commands
received by the SR510. It also does not affect the
terminating sequence sent with data over the
GPIB interface.
The SR510 with the GPIB
Interface
For a brief introduction to the GPIB standard,
please read Appendix C at the back of this
manual. Before using the GPIB interface you
must set the switches in SW1 per the instructions
on page 7.

GPIB Capabilities

The GPIB capabilities of the SR510 consistent
with IEEE standard 488 (1978) are shown in the
table below. Also shown are the responses of the
SR510 to some standard commands.
Code Function
SH1 Source handshake capability
AH1 Acceptor handshake capability
T5 Basic Talker, Serial Poll, Unaddressed to
talk if addressed to listen
L4 Basic Listener, Unaddressed to listen if
addressed to talk
SR1 Service request capability
PP0 No parallel poll capability
DC1 Device Clear capability
RL0 REN,LLO, GTL not implemented.
'I' command sets Remote-Local.
SR510 Response to GPIB Commands
Mnemonic Command
DCL Device Clear
SDC Selected
Device Clear
SPE Serial Poll
Enable
Because the SR510 can be controlled by an
RS232 interface as well as the GPIB, the remote-
local functions are not standard. There is no local
with lock out state. When in the local state,
remote commands are processed, even without
the REN command being issued. This is because
22
Response
Same as Z command
Same as Z command
Send Status Byte,
& clear status byte