The Status Byte
Group’s Enable
Register
The Enable Register for the Status Byte Group has a special purpose.
Notice in Figure 4-6 how the Status Byte Summary bit wraps back around to
the Status Byte. The Summary bit sets the RQS (request service) bit in the
Status Byte. Using this Summary bit (and those from the other status
groups) you can poll the Status Byte and check the RQS bit to determine if
there are any status conditions which need attention. In this way the RQS
bit is like the HP-IB’s SRQ (Service Request) line. The difference is that
while executing an HP-IB serial poll (SPOLL) releases the SRQ line,
executing the
*STB?
command does not clear the RQS bit in the Status
Byte. You must read the Event Register of the group who’s Summary bit is
causing the RQS.
Reading Status
Groups Directly
You may want to directly poll Status Groups for instrument status rather
than poll the Status Byte for summary information.
Reading Event
Registers
The Questionable Data, Operation Status, and Standard Event Groups all
have Event Registers. These registers log the occurrence of even temporary
status conditions. When read, these registers return the sum of the decimal
values for the condition bits set, then are cleared to make them ready to log
further events. The commands to read these Event Registers are:
STAT:QUES:EVEN?
Questionable Data Group Event
Register.
STAT:OPER:EVEN?
Operation Status Group Event
Register.
*ESR?
Standard Event Group Event
Register.
Clearing Event
Registers
To clear the Event Registers without reading them execute:
*CLS
Clears all group’s Event
Registers.
Reading Condition
Registers
The Questionable Data and Operation Status Groups each have a Condition
Register. The Condition Register reflects the group’s status condition in
“ real-time” . These registers are not latched so transient events may be
missed when the register is read. The commands to read these registers are:
STAT:QUES:COND?
Questionable Data Group
Condition Register.
STAT:OPER:COND?
Operation Status Group
Condition Register.
128 Understanding the HP E1313/E1413
Chapter 4
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