Valhalla Scientific 4300B, Operation Manual

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5-7. Remote and Local States
¾ Local State
When the 4300B is in the "local" state the REMOTE indicator on the front panel is extinguished and full
manual control as described in Section 4 may be performed. The user should also note that the 4300B will
ignore commands from the GPIB while in the local state.
The 4300B automatically powers-up in the local state. Other methods for placing it in the local state are by
cycling power or by sending a
return to local (RTL) command over the bus. This is done in HP Basic using
the command: LOCAL 712
To ensure compatibility with all controllers, the 4300B may also be returned to the local state by sending it the
code:
L
¾ Remote State
In this state the REMOTE indicator on the front panel is illuminated and all controls on the front panel are
disabled except the power switch.
The remote state may only be entered via the bus. If the 4300B receives its listen address while the REN line
is asserted, it will enter the remote state. Placing the instrument into remote is an easy way of verifying that all
connections and address selections have been done properly. This may be accomplished in HP Basic using
the command:
REMOTE 712 The 4300B should enter the remote state and illuminate the REMOTE
indicator. Verify that no other device on the bus was affected by execution of this command.
5-8. Reading the Display Data
The resistance data on the 4300B's display is always available to be read by the system controller. The 4300B
does not require that a query or any other command be issued in order to retrieve it. Also, the 4300B does not
need to be in REMOTE in order for the display to be read. Retrieving the data will clear the reading buffer.
The controller must then wait until the next update of the A-to-D converter before a new value becomes
available. Data may be read at the rate of 2½ readings per second for a 4300B, or 12½ readings per second for
a 4350ATE.
The fact that the readings are always available simplifies measurement retrieval. Every time the system
controller polls the 4300B's address, an instantaneous resistance value is returned corresponding to the
displayed value.
The following program shows an example of retrieving a resistance measurement from the 4300B. The
program is written in HP Basic. If you are using a programming language or package other than HP Basic,
consult your Programmer's Manual for the correct command syntax. The 4300B is assumed to be at address
12.
10 ENTER 712;A$
20 PRINT A$
30 GOTO 10
40 END