R&S ZVL
Remote Control
Status Reporting System
Operating Manual 1303.6580.32-05
343
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 Visual 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
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:
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.
Bits
Weight
0
1
2
3
4
5
6
7
...
1
2
4
8
16
32
64
128
...
Example:
The decimal value 40 = 32 + 8 indicates that bits no. 3 and 5 in the status register (e.g. the
QUEStionable status summary bit and the ESB bit in the STatus Byte) are set.
Queries are usually used after an SRQ in order to obtain more detailed information on the cause of the
SRQ.
