Rohde & Schwarz 1145.1010.04/05/06, Operating Manual

Page: 457 / 813

R&S
®
ZVA/ZVB/ZVT Status Reporting System
1145.1084.12 5.25 E-1
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?
.
Serial poll procedure
The serial poll method is defined in IEEE 488.1 and used to be the only standard possibility 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 quick BASIC command for executing a serial poll is "IBRSP()".
The serial poll is mainly used to obtain a fast overview of the state of several instruments connected to
the GPIB bus.
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".
Parallel poll procedure
In addition to the SRE register, which determines the conditions under which an SRQ is generated,
there is a Parallel Poll Enable register (PPE) which is ANDed with the STB bit by bit, considering bit 6 –
AND as well. 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 instrument first has to be set for the parallel poll using the quick BASIC command "IBPPC()". This
command allocates a data line to the instrument and determines whether the response is to be
inverted. The parallel poll itself is executed using "IBRPP()".
The parallel poll method is mainly used to find out quickly which one of the instruments connected to
the GPIB bus 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:
•
The common commands *ESR?, *IDN?, *IST?, *STB? query the higher-level registers.
•
The commands of the STATus system query the SCPI registers (STATus:QUEStionable...)
All queries return a decimal number which represents the bit pattern of the status register. This number
is evaluated by the controller program.
Decimal representation of a bit pattern
The STB and ESR registers contain 8 bits, the SCPI registers 16 bits. The contents of a status register
is keyed and transferred as a single decimal number. To make this possible, each bit is assigned a
weighted value. The decimal number is calculated as the sum of the weighted values of all bits in the
register that are set to 1.