Rohde & Schwarz SMBV100A, Руководство пользователя

Страница: 447 / 780

Remote Control Basics
R&S
®
SMBV100A
430 Operating Manual 1407.6062.32 ─ 08
6.5.5.2 Serial Poll
In a serial poll, just as with command
*STB
, the status byte of an instrument is queried.
However, the query is realized via interface messages and is thus clearly faster.
The serial poll method is defined in IEEE 488.1 and used to be the only standard possi-
bility for different instruments to poll the status byte. The method also works for instru-
ments 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 instruments
connected to the controller.
6.5.5.3 Parallel Poll
In a parallel poll, up to eight instruments are simultaneously requested by the controller
using 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) which is ANDed with the STB
bit by bit, considering bit 6 as well. This register is ANDed with the STB bit by bit, con-
sidering 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 using the command
​
*IST
​
.
The instrument first has to be set for the parallel poll using the command
PPC
. This com-
mand allocates a data line to the instrument and determines whether the response is to
be inverted. The parallel poll itself is executed using
PPE
.
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.
6.5.5.4 Query of an instrument status
Each part of any status register can be read using queries. There are two types of com-
mands:
●
The common commands
*ESR?
,
*IDN?
,
*IST?
,
*STB?
query the higher-level reg-
isters.
●
The commands of the
STATus
system query the SCPI registers
(
STATus:QUEStionable
...)
The returned value is always a decimal number that represents the bit pattern of the
queried register. This number is evaluated by the controller program.
Queries are usually used after an SRQ in order to obtain more detailed information on
the cause of the SRQ.
Status Reporting System