Rohde & Schwarz PR100 - Structure of an SCPI Status Register; Condition Section; Ptransition Section

R&S PR100 User Manual
The STB receives information from the other registers and evaluates whether
an SRQ or IST message has to be generated: The IST flag ("Individual
STatus") and the “parallel poll enable” register (PRE) allocated to it are also
part of the status reporting system. The IST flag, like the SRQ, combines the
entire device status in a single bit. The PRE fulfils a function for the IST flag
as the SRE does for the service request.
For SCPI over TCP/IP, an SRQ is a text-response “&SRQ<CR><LF>”, where
<CR> is a carriage-return, and <LF> is a line-feed. A C-type string would read
as: “&SRQ\r\n”.
The message queue contains the messages the device sends back to the
controller. It is not part of the status reporting system but determines the value
of the “message available” (MAV) bit in STB and is thus shown in Section
9.2.2.2.
Structure of an SCPI status register
Each SCPI register consists of 5 sections each having a width of 16 bits (see
Figure 2). Bit 15 (the most significant bit) is set to zero for all sections. Thus
the contents of the register sections can be processed by the controller as
positive integers. The function of each section is explained below.
CONDition section
The CONDition section of a register reflects directly the state of the hardware.
This register section can only be read. Its contents are not changed during
reading. As an alternative, a bit in a CONDition register can also contain the
summary information of a further status register connected in front. In this
case, the bit is cleared only when reading out the root-cause of the bit:
another bit in another status register connected in front.
PTRansition section
The Positive-TRansition section acts as an edge detector. When a bit of the
CONDition section is changed from 0 to 1, the associated PTR bit decides
whether the EVENt bit is set to 1.
PTR bit = 1: the EVENt bit is set.
PTR bit = 0: the EVENt bit is not set.
This section can be written into and read from in any way. Its contents are not
changed during reading.