R&S®SML / R&S®SMV03 Status Reporting System
1090.3123.12 E-6 5.23
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, ie to set the data line allocated to
each instrument to logically "0" or "1". Analogously to the SRE register, which determines under what
conditions an SRQ is generated, there is a parallel poll enable (PPE) register, which is likewise ANDed
with the STB bit by bit, with bit 6 being taken into account. The results are ORed, and the result of this is
sent (possibly inverted) in response to a parallel poll by the controller. The result can also be queried
without a parallel poll using the command *IST.
The instrument first has to be set for parallel polling by means of the QuickBASIC 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 in order to find out quickly, after an SRQ, which instrument has
sent the service request if there are many instruments connected to the IEC/IEEE bus. To this effect,
the SRE and the PPE must be set to the same value. A detailed example on parallel polling will be found
in chapter 7, "Programming Examples".
Query by Means of Commands
Each part of every status register can be read by means of a query. The queries to be used are included
with the detailed description of the registers. In response to a query, a number is always returned which
represents the bit pattern of the register queried. The number is evaluated by the controller program.
Queries are normally used after an SRQ to obtain more detailed information on the cause of the SRQ.
Error Queue Query
Each error state in the instrument leads to an entry in the error queue. The entries to the error queue are
detailed plain-text error messages which can be displayed in the Error menu by manual control or
queried via the IEC/IEEE bus with the command SYSTem:ERRor?. Each call of SYSTem:ERRor?
provides one entry from the error queue. If no more error messages are stored there, the instrument
responds with 0, ie "No error".
The error queue should be queried by the controller program after each SRQ as the entries provide a
more precise description of the cause of an error than the status registers. Especially during the test
phase of a controller program the error queue should be queried regularly since errored commands
from the controller to the instrument are also recorded in the error queue.
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