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Chapter 4, Status Reporting
Status Reporting
Event Register
The Event Register captures bit-state transitions in the Condition Register as
defined by the Transition Filters. Each bit in the Event Register corresponds to a
bit in the Condition Register, or if there is no Condition Register/Transition Filter
combination, each bit corresponds to a specific condition in the Test Set. Bits in
the Event Register are latched, and, once set, they remain set until cleared by a
query of the Event Register or a *CLS (clear status) command. This guarantees
that the application can't miss a bit-state transition in the Condition Register.
There is no buffering; so while an event bit is set, subsequent transitions in the
Condition Register corresponding to that bit are ignored. Event Registers are read-
only. Event Registers in the Test Set are either 8 or 16 bits long and may contain
unused bits. All unused bits return a zero value when read.
Event Enable Register
The Event Enable Register defines which bits in the Event Register will be used to
generate the Summary Message. Each bit in the Enable Register has a
corresponding bit in the Event Register. The Test Set logically ANDs
corresponding bits in the Event and Enable registers and then performs an
inclusive OR on all the resulting bits to generate the Summary Message. By using
the enable bits the application program can direct the Test Set to set the Summary
Message to the 1 or TRUE state for a single event or an inclusive OR of any group
of events. Enable Registers are read-write. Enable Registers in the Test Set are
either 8 or 16 bits long and may contain unused bits which correspond to unused
bits in the associated Event Register. All unused bits return a zero value when read
and are ignored when written to. Enable Registers are unaffected by a *CLS (clear
status) command or queries.
Summary Message Bit
The Summary Message is a single-bit message which indicates whether or not one
or more of the enabled events have occurred since the last reading or clearing of
the Event Register. The Test Set logically ANDs corresponding bits in the Event
and Enable registers and then performs an inclusive OR on all the resulting bits to
generate the Summary Message. By use of the enable bits, the application
program can direct the Test Set to set the Summary Message to the 1, or TRUE,
state for a single event or an inclusive OR of any group of events. The Summary
Message is TRUE when an enabled event in the Event Register is set TRUE.
Conversely, the Summary Message is FALSE when no enabled events are TRUE.
Summary Messages are always seen as bits in another register.
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