Specifications

SR400 with the GPIB Interface
53
SR400 WITH THE GPIB INTERFACE
Before using the GPIB interface you must set the
GPIB address in the COM menu.
GPIB CAPABILITIES
The GPIB capabilities of the SR400 consistent
with IEEE standard 488 (1978) are shown in the
table below. Also shown are the responses of the
SR400 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
RL1 REN,LLO, GTL implemented
DT1 GET implemented
SR400 Response to GPIB Commands
Mnemonic
Command Response
DCL Device Clear
Same as CL command
SDC Selected Device Clear
Same as CL command
SPE Serial Poll Enable
Send Status Byte after service
request
GET Group Execute Trigger
Same as CS command
The SR400 will respond to commands only if it is
addressed to listen and the Remote Enable line
(REN) is asserted. When this occurs,the front
panel goes to the REMote state;the knob and all of
the keys except for the COM/LOCAL key are
disabled. The COM/LOCAL key will return the
unit to the LOCAL state. The COM/LOCAL key
may be locked out by asserting the Local-Lockout
state (LLO).
SERIAL POLLS AND SERVICE
REQUESTS
The SR400 can be programmed to generate a
service request (SRQ) to the GPIB controller
every time a given status condition occurs. This is
done using the SV{j} command. The mask value, j
(0-255), is the SRQ mask byte. The mask byte is
always logically ANDED with the status byte. If
the result is non-zero, the SR400 generates an
SRQ and leaves the status byte unchanged until
the controller performs a serial poll to determine
the cause of the service request. For example, if
we want to generate an SRQ at the end of a scan,
we need an SRQ mask byte equal to 00000100
binary, or 4 decimal ("SV4" command). The byte
00000100 binary corresponds to the status byte
with the 'scan finished' status bit set. When the
next end of scan occurs, an SRQ will be generated.
The serial poll will return a status byte showing
SRQ and scan finished (01000100 binary or 68
decimal). When a service request is generated, the
corresponding bit in the SRQ mask byte is reset.
This will prevent an uncontrolled stream of service
requests from continually interrupting the
controller. To re-enable the service requst, the
controller must again set the service request mask
with the SV command.
Serial Polls performed without a service request
return all status conditions which have ocurred
since the last time the status byte was cleared.
Note that the serial poll does not clear the status
byte. To clear the status byte use the SS command.
EXAMPLE PROGRAMS
The following section lists several example
programs which use the GPIB port to control the
SR400. All of the programs do the same thing,
only the language is different. The programs set up
the SR400 to count 10 MHz on counter A for 1
second. The counter data is read and the PORT1
output is ramped.