By analogy with the SRQ, the IST flag combines the entire status information
in a single bit. It can be queried by means of a parallel poll (cf. Section
Parallel Poll) or using the command "*IST?".
The parallel poll enable register (PPE) determines which bits of the
STB contribute to the IST flag. The bits of the STB are ANDed with the
corresponding bits of the PPE, with bit 6 being used as well in contrast
to the SRE. The IST flag results from the ORing of all results. The PPE
can be set using commands "*PRE" and read using command "*PRE?".