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Section 5 Remote Control
5-24
The status model uses an IEEE 488.1 status byte. This status byte consists of
seven summary message bits provided by the status data structure. To generate
these summary message bits, the status data structure is comprised of two models:
a register model and a queue model.
Register model
A pair of registers used to record an event that a device has encountered and a
condition. It consists of an event status register and an event status enable regis-
ter. When the results of ANDing the values of bits of these registers is not 0, the
corresponding status register bits are set to 1s. In other cases, the corresponding
status register bits are set to 0s. If the result of ORing the values of status register
bits is 1, the summary message bit is set to 1. If the result of ORing these bits is 0,
the summary message bit is set to 0.
Queue model
A data structure in which status values or information are removed in the same
order of which those were entered. Only when the queue structure contains data,
the corresponding bit is set to 1. If it is empty, the corresponding bit is set to 0.
Based on the concept of the above register model and queue model, the IEEE
488.2 standard status model is constructed from two types of register models and
a queue model.
(1) Standard event status register and standard event status enable
register
This register has the register model structure mentioned above. It has eight
bits corresponding to eight standard events listed below encountered by the
device.
(a) power on
(b) user request
(c) command error
(d) execution error
(e) device dependent error
(f) query error
(g) bus control request
(h) operation complete.
The result of logical OR is output to the status byte register bit 5 (DIO 4) as
an event status bit (ESB) summary message.