Gated Integrators and Boxcar Averagers
SR245 — Computer interface module with GPIB and RS-232· Eight analog I/O ports· 8-bit digital I/O port
· Two TTL I/O ports· RS-232 and GPIB interfaces· 3500 point sample memory· Simple command structure· SR245 ... $1500 (U.S. list)

SR245 Computer Interface
The SR245 Computer Interface module is a powerful toolfor data acquisition. It provides both an analog and a digitalinterface between your computer and your experiment.
Analog I/O
The eight analog I/O channels can be designated throughsoftware as all inputs, all outputs, or as a combination ofinputs and outputs. All channels have 13 bits of resolution
over the ±10.24 VDC full-scale range, with 0.05 % accuracy.
Digital I/O
Two front-panel digital I/O bits are provided for use as
counters or triggers and can be set or read by the computer.
Additionally, an 8-bit input and an 8-bit output port areavailable (on an internal connector) for your own custom
digital interfaces.

Stanford Research Systems

RS-232 and GPIB interfaces
Both RS-232 and GPIB interfaces are standard features ofthe SR245. Simple commands make programming easy froma variety of high-level languages—all that’s necessary is
the ability to send and receive ASCII strings. For example,
sending “?5” instructs the module to measure the voltage
on the 5th analog input BNC. Other commands allow you torecord in the module’s 3500 point buffer memory, ramp ananalog output at a specified rate (for gate scanning), or readthe contents of a digital counter.

Ordering Information
SR245

Computer interface moduleSR245 Specifications

Analog Ports
Configuration

Inputs

Outputs

Any number of the eight ports may
be designated under program
control as input ports, the rest
default to output ports.
1 MΩ impedance±10.24 VDC range (protected to 40 VDC)
13-bit resolution (2.5 mV)
0.5 % accuracy
Input offset <2.5 mVMaximum A/D rate is 2 kHz<1 Ω impedance. Short circuitcurrent limit is 20 mA.
13-bit resolution (2.5 mV)
0.5 % accuracy
Output offset <2.5 mV

SB<n>=<m>SB<n>=I
SD=<n>
SM=<n>
Trigger Commands
MSMADigital Ports
Type
Front-panel inputs

Front-panel outputs

Two front-panel I/O TTL bits, one
8-bit digital input port, one 8-bit
latched digital output port
Input impedances >100 kΩ
Minimum pulse width is 200 ns
Maximum count rate is 4 MHz
Logic one >3 VDC, logic zero <0.7 VDC
Inputs protected to ±10 VDC
Can drive 50 Ω loads to TTL levels

T<n>
DTET
PB<n>
P/<n>

Interfaces

IEEE-488 (GPIB) and RS-232(110 baud to 19.2 kbaud)+24 V/60 mA, 24 V/60 mA,+12 V/20 mA, approx. 8 watts
Single-width standard NIM module
One year parts and labor on defects
in materials and workmanshipPowerMechanical
WarrantyCommand List

SC<i>,<k>:<n>ESN?N
A<n>,<i>Input/Output Commands
SS<i>,<k>:<n>
I<n> n=0 to 8?<n> n=1 to 8?B<n> n=1,2?S
C?C
S<n>=<x>

Sets the synchronous mode.
Responses to ? commands arereturned after next trigger.
Sets the asynchronous mode
(default). Responses to ? commands
are returned after commandis received.
Designates every nth pulse at B1 asa trigger (n = 1 to 32,767)
Masks the trigger input so that notriggers are recognizedUnmasks the trigger input
Outputs a 10 µs TTL pulse at digital
port n (n = 1, 2)
Outputs a 10 µs TTL pulse at B2
each nth trigger (n = 1 to 255)

Scan Commands

General?Dvalue x (x = –10.237 V to +10.237 V)
n = 1 to 8
Designates digital bit n as output
and sets its value to m (n = 1, 2 andm = 0, 1)
Designates the selected bit as aninput (n = 1, 2)
Sets the 8-bit digital output port tothe value n (n = 0 to 255 )Sets the GPIB SRQ mask to thevalue n (n = 0 to 255)

Designates the first n analog portsas inputs, the remainder become outputs
Returns the value of the designatedanalog port
Returns the value (0 or 1) of thedesignated digital port
Returns the value of the 8-bit
digital input port
Returns the value of the status byte,
and clears the status byte
Configures B2 as an input andresets the B2 counter
Returns number of pulses occurring
at B2 since the previous ?C
Sets the analog port n (which must
be designated as an output) to the

Stanford Research Systems

X

Scans the list i..k of analog ports ordigital port for n triggers. Total #of samples may not exceed 3711.
(i..k = 1 to 8, D)
Ends the current scan immediately
and resets the point sending counter
Sends the next point of stored scan
Returns # of points scanned
Adds n × 2.5 mV to the value of
analog port 8 (must be positive)on every ith trigger (n,i = 1 to 255)
Scans the list i..k of analog ports ordigital port for n triggers. Data issent in a 2 byte binary format while
scan is in progress.(i..k = 1 to 8, D)
Sends the data of a stored scan in
2 byte binary formatMiscellaneous CommandsMRW<n>Z<i>,<k>Master reset returns the SR245
to its default values.
Introduces a delay of (n × 400 µs)
before sending each character overthe RS-232 interface (n = 0 to 255)
Changes the end-of-record
characters sent by SR245 to thosespecified by the ASCII codes, i...k