Types Of Status Information Available - Fluke 8508A User Manual

Standard-Defined and Device-Specific Features
In the 8508A, the structure has three main registers, as follows:
The Status Byte Register, and its associated enable register, control the generation
of the Status Byte, which summarizes the remainder of the status structure.
The Event Status Register, and its associated enable register, control the generation
of the Event Status Byte, whose component bits report Standard-defined types of
events. This register is summarized by the ESB bit 5 in the Status Byte.
The Measurement Event Status Register, and its associated enable register, control
the generation of the Measurement Event Status Byte, whose component bits
relate to measurement events in the 8508A. It is summarized by the MES bit 0 in the
Status Byte.
In the Event Status Byte the EXE bit is associated with a queue of execution errors
related to the 8508A programmed condition, and the DDE bit is associated with a queue
of device-dependent errors related to 8508A internal faults.
A Note about Queues. These are 'historical' (Last-in - Last Out) stacks, and
when the queue stack is full the eldest entries are discarded. It is
recommended that the application read the queue as soon as its summary bit
is set true, particularly the error bits, otherwise the original cause of the
error can be discarded as subsequent dependent errors fill up the stack.
However any message indicated by the MAV bit should be read before
attempting to obtain the ESR status byte.
Access via the Application Program
The application designer has access to three enable registers to enable or disable any
individual bit in these registers.
Thus the application programmer can decide which assigned events will generate an
SRQ, by enabling their event bits and then enabling the appropriate summary bit(s) in the
Status Byte. The Controller can be programmed to read the Status Byte during a
resulting serial poll, and be directed to the appropriate Event Register to discover which
event was responsible for originating the SRQ.

Types of Status Information Available

Status Summary Information
The Status Byte (STB) consists of flag bits which direct the Controller's attention to the
type of event which has occurred.
Standard-defined events
The following events are flagged in the 8-bit latched Event Status Register (ESR), read-
accessible to the controller.
Power On - the instrument's power supply has been switched on.
User Request - This capability is not available in the 8508A.
Command Error - a received bus command does not satisfy the syntax rules
programmed into the instrument interface's parser, and so is not recognized as a valid
command.
Execution Error - a received command has been successfully parsed, but it cannot be
executed owing to the current programmed condition of the instrument.
Remote Operations Using the IEEE 488 Interface
Using the 8508A Reference Multimeter in a System
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