F.W. Bell 7030, Instruction Manual

Page: 81 / 126

F.W. BELL Model 7030 Gauss/Tesla Meter Instruction Manual
Section 7 – Remote Operation 7-7
IEEE-488
GENERAL BUS
COMMANDS
(Continued) DCL - DEVICE CLEAR
This command clears the bus and returns it to a known state. All
devices are affected. The instrument will cancel any pending
commands and clear its output buffers. Instrument settings are not
affected.
SDC - SELECTIVE DEVICE CLEAR
Same as the DCL command except only for the addressed instrument.
SPE,SPD - SERIAL POLL
This command obtains the serial poll status byte, which contains
important status information about the instrument. Often a serial poll is
initiated when one or more devices are asserting an interface line called
SRQ (service request).
ERROR QUEUE AND
OUTPUT QUEUE
Internally there are two buffers that accumulate messages. Errors are
generated by a variety of sources, such as hardware errors or errors in
the command syntax. As errors occur messages are stored in an
ERROR QUEUE. They can be read by specific commands discussed
later in this section.
Any time a command requests information from the instrument, such as
flux density readings, instrument status or error messages, the
information is placed in the OUTPUT QUEUE. They can be read by the
system controller using a standard INPUT command.
STATUS There are four register sets that indicate the status of the instrument,
such as errors or the present state of the machine. These are 16-bit
registers, but in many cases not all of the bits are used. The four
register sets are called:
MEASUREMENT EVENT OPERATION EVENT
STANDARD EVENT QUESTIONABLE EVENT
There is also an 8-bit register that provides a 1-bit summary for each of
the four register sets. This is called the STATUS BYTE.