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SECTION 6 GPIB
6-21
6.5.2 IEEE488.2-based status register
IEEE488.2 prescribes the following two status registers.
Status byte register Used to set the RQS and seven summary bits. Combined with a service
request enable register. SRQ bit is set on when ORs of both the status and
service request enable registers are not 0. RQS, reserved in bit 6, indicates
whether a service request is in an external controller.
Standard event status register Used to set eight types of standard events the device encounters. The
logical OR output bit is summarized in bit 5 of the status byte register as a
summary message of the event status bit (ESB).
Standard Status Model Diagram
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
&
&
&
&
&
&
&
&
7
5
4
3
2
1
0
7
6
5
4
3
2
1
0
&
&
&
&
&
&
&
Standard event
status enable
register
Logical OR
Power-on (PON)
User request (URQ)
Command error (CME)
Execution-time error (EXE)
Device dependent error (DDE)
Query error (QYE)
Bus control right request (RQC, not used)
End of operation (OPC)
Standard event
status register
Set by *ESE<n>
Read by *ESE?
Read by * ESR?
Data
Data
Data
Data
Data
Service request
occurrence
Logical OR
Output queue
Status
summary
message
OPER
ESB
MAV
QUES
QUE
NOT USED
NOT USED
MSS RQS
Service request
enable register
Set by *SRE<n>
Read by * SRE?
Read by *STB?
Status byte
register
Read by serial pole