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Query Error Register - GPIB IEEE Std. 488.2 Error Handling
These errors are much more likely to occur on the semi-duplex GPIB interface, which requires
the instrument to hold a response until addressed to talk by the controller. All the other
interfaces provide full duplex communication, with buffering in the physical layer which will
usually hold a response from the instrument until the controlling software reads it; there is no
equivalent of the GPIB state ‘addressed to talk’, so the instrument is not aware of the actions of
the controller
The IEEE 488.2 UNTERMINATED error arises if the instrument is addressed to talk and has
nothing to say, because the response formatter is inactive and the input queue is empty. This
will cause the Query Error bit to be set in the Standard Event Status Register, a value of 3 to be
placed in the Query Error Register and the parser to be reset.
The IEEE 488.2 DEADLOCK error arises if the response formatter is waiting to send a
response message and the input queue becomes full. This will cause the Query Error bit to be
set in the Standard Event Status Register, a value of 2 to be placed in the Query Error Register
and the response formatter to be reset, discarding the waiting response message. The parser
will then start parsing the next <PROGRAM MESSAGE UNIT> from the input queue.
The IEEE 488.2 INTERRUPTED error arises if the response formatter is waiting to send a
response message and a <PROGRAM MESSAGE TERMINATOR> has been read by the
parser, or the input queue contains more than one END message. This will cause the Query
Error bit to be set in the Standard Event Status Register, a value of 1 to be placed in the Query
Error Register and the response formatter to be reset, discarding the waiting response
message. The parser will then start parsing the next <PROGRAM MESSAGE UNIT> from the
input queue.
Power on Settings
The following instrument status values are set at power on:
EER
Execution Error Register
= 0
ESR
Standard Event Status Register
= 128 (pon bit set)
QER
Query Error Register †
= 0
ESE
Standard Event Status Enable Register †
= 0
STB
Status Byte Register
= 0
SRE
Service Request Enable Register †
= 0
PRE
Parallel Poll Response Enable Register †
= 0
†
Registers marked thus are normally only used through the GPIB interface.
The instrument will be in local state with the keyboard active. By default, the instrument settings
at power on are the same as at the last switch off and the outputs are off. These parameters
may be configured by the user to allow outputs to be the same as at the last switch off or,
alternatively, all settings and outputs may be reset to factory defaults at power on, see 10.1.
Register Summary
Set
Query
Name
LSR1?, LSR2?, LSR3?
Limit Status Registers
LSE1, LSE2, LSE3
LSE1?, LSE2?, LSE3?
Limit Status Enable Registers
††
EER?
Execution Error Register
††
QER?
Query Error Register
††
*ESR?
Standard Event Status
Register
(continued)
††
These registers are cleared after being queried, or by the *CLS command.
