15
Remote Interface Operation
(CPX200DP only)
The instrument can be remotely controlled via its RS232, USB, LAN or GPIB interfaces.
USB remote control operates in a similar way to RS232 but via the USB connector. Software
supplied with the instrument sets up the controlling computer to treat the USB connection as a
virtual COM port. Application software on the computer can then access the instrument via that
COM port.
The LAN interface is designed to meet 1.4 LXI ( Lan eXtensions for Instrumentation) Core 2011.
Remote control using the LAN interface is possible using the TCP/IP Sockets protocol. The
instrument also contains a basic Web server which provides information on the unit and allows it to
be configured from a web browser. Simple command line control from the browser is also
possible.
All interfaces are, by default, live at all times (a LXI requirement) but access to individual interfaces
may be restricted using the configuration options on the web pages.
Interface Locking
All the remote interfaces are live at all times, to remove any need to select the active interface and
to ensure that the LAN interface is always available (as demanded by the LXI standard). To reduce
the risk of the instrument being inadvertently under the control of two interfaces at once a simple
lock and release mechanism is provided in the instruction set. The lock is automatically released
where it is possible to detect disconnection and when the local button is pressed. Access to the
interfaces may also be restricted using the web pages.
Any interface may request to have exclusive control of the instrument by sending an “IFLOCK”
command. The lock may only be released by sending an “IFUNLOCK” command from the interface
instance that currently has the lock and may be queried from any interface by sending an
“IFLOCK?” command. The reply to any of these commands will be “-1” if the lock is owned by
another interface instance, “0” if the interface is free and “1” if the lock is owned by the requesting
interface instance. Sending any command from an interface without control privileges that
attempts to change the instrument status will set bit 4 of the Standard Event Status Register and
put 200 into the Execution Error Register to indicate that there are not sufficient privileges for the
required action.
Note:
it is also possible to configure the privileges for a particular interface to either ‘read only’ or
‘no access’ from the Web page interface.
Address Selection
The instrument address capability is strictly required only by the GPIB interface. However, use can
be made of the ADDRESS? command over any of the interfaces to easily identify which instrument
is being controlled by a particular COM port (for RS232 or USB) or TCP socket (for LAN). Note
that the LAN interface also has a separate ‘Identify’ function, accessible from the instrument’s web
pages, that flashes the instrument’s display until the function is cancelled.
The address is set from the instrument’s front panel as follows. Start with the instrument off and,
with the VIEW and LOCK keys of Output 1 both held down, switch the instrument on. The display
will show
Addr
in the Volts display and
nn
in the
Amps display where
nn
is the present
setting (default
Addr
11
).
The address can be decremented and incremented by the VIEW and
LOCK keys respectively in the range 1 to 31 inclusive (not 0), with 'wrap-round'. The address is
confirmed and the process exited by holding down the OVP key; the display will show
SEt
and
the new address for approximately 2 seconds, returning to the normal Volts and Amps display
when the new address has been accepted.
The address can also be set from the instrument’s web pages.
