Parallel poll
Note, that the sophisticated parallel poll function is only useful with GPIB interfaces and requires traditional GPIB drivers.
In a parallel poll, the controller requests up to eight instruments to set the data line allocated to each instrument to a logical "0" or "1".
The SRE register determines the conditions under which an SRQ is generated. In addition, there is a parallel poll enable register (PPE). This register is combined with the status byte (STB) by a logical AND operation bit by bit, considering bit 6 as well. The results are combined by a logical OR operation. 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 *IST? command.
Initially, you must configure the instrument to use the parallel poll using the PPC command. This command allocates a data line to the instrument and determines whether the response is to be inverted. To execute the parallel poll itself, use PPE.
See also "IST flag and PPE".
The parallel poll method is used to find out quickly which of the instruments connected to the controller sent a service request. To this effect, SRE and PPE must be set to the same value.