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B.9 The SCPI Status Reporting
Status registers provide the status mechanism described in IEEE488.2. And there are three
register groups with various equipment conditions recorded by the status system. They are the
Status Byte Register, the Standard Event Register and the Questionable Data Register. The
Status Byte Register collects and records high-level summary information which is reported in
other register groups. With the following diagram illustration, users would make themselves
clear for the SCPI status system.
In addition, the Standard Event and the Questionable Data Registers have event registers
which belong to read-only registers and report defined conditions in a multimeter. Bits are
latched in the event registers. As long as an event bit is set, subsequent state changes will be
ignored. To query an event register will return a decimal value corresponding to
binary-weighted sum of all bits set in the register.
An enable register is readable and writable, and can define which bits in the corresponding
event register are ORed together to generate a single summary bit. To query an enable
register won’t clear it, as well the command *CLS, but it can clear the bits in the event
registers. Moreover, to enable bits in an enable register, users have to write a decimal value
corresponding to the binary-weighted sum of the bits in the register by their demands.
Binary Weights
2º = 1
2¹ = 2
2² = 4
2³ = 8
2
4
= 16
2
5
= 32
2
6
= 64
2
7
= 128
2
8
= 256
2
9
= 512
2
10
= 1024
2
11
= 2048
2
12
= 4096
2
13
= 8192
2
14
= 16384
2
15
= 32768
