Command Reference
R&S
®
ZNL/ZNLE
578
User Manual 1178.5966.02 ─ 07
Example: Find out which event caused an SRQ
The procedure to find out which event caused an SRQ is analogous the procedure to
generate an SRQ:
1.
STB?
(query the contents of the status byte in decimal form)
If bit 3 (QUEStionable summary bit) is set, then:
2.
STAT:QUES:EVENT?
(query STATus:QUEStionable register)
If bit 10 (QUEStionable:LIMit1 summary bit) is set, then:
3. Query
STAT:QUES:LIMit1:EVENT?
(query
STATus:QUEStionable:LIMit1
register)
If bit 1 is set, then the first trace failed the limit check.
The SRQ is the only possibility for the instrument to become active on its own. Each
controller program should set the instrument such that a service request is initiated in
the case of malfunction. The program should react appropriately to the service request.
Serial Poll
In a serial poll, the controller queries the STatus Bytes of the devices in the bus system
one after another. The query is made via interface messages, so it is faster than a poll
by means of
*STB?
.
The serial poll method is defined in IEEE 488.1 and used to be the only standard pos-
sibility for different instruments to poll the status byte. The method also works for
instruments which do not adhere to SCPI or IEEE 488.2.
The serial poll is mainly used to obtain a fast overview of the state of several instru-
ments connected to the controller.
Parallel Poll
In a parallel poll, up to eight instruments are simultaneously requested by the controller
by means of a single command to transmit 1 bit of information each on the data lines,
i.e., to set the data line allocated to each instrument to a logical "0" or "1".
In addition to the SRE register, which determines the conditions under which an SRQ
is generated, there is a Parallel Poll Enable register (PPE) . This register is ANDed
with the STB bit by bit, considering bit 6 as well. The results are ORed, the result is
possibly inverted and then sent as a response to the parallel poll of the controller. The
result can also be queried without parallel poll by means of the command
*IST?
.
The parallel poll method is mainly used to find out quickly which one of the instruments
connected to the controller has sent a service request. To this effect, SRE and PPE
must be set to the same value.
Query of an Instrument Status
Each part of any status register can be read by means of queries. There are two types
of commands:
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