HP E4401B, Programmer'S Manual

Page: 33 / 398

Chapter 2 2-3
HP ESA Status Registers
Using the Analyzer Status Registers
1. Determine which register contains the bit that reports the condition.
2. Send the unique SCPI query that reads that register.
3. Examine the bit to see if the condition has changed.
Using the Status Registers
Most monitoring of the analyzer conditions is done at the highest level
using the IEEE common commands indicated below. Complete
command descriptions are available in the IEEE commands section at
the beginning of the language reference:
*CLS
(clear status) clears the status byte by emptying the error
queue and clearing all the event registers.
*ESE
,
*ESE?
(event status enable) sets and queries the bits in the
enable register part of the standard event status register.
*ESR?
(event status register) queries and clears the event register
part of the standard event status register.
*OPC
,
*OPC?
(operation complete) sets the standard event status
register to monitor the completion of all commands. The query stops
any new commands from being processed until the current
processing is complete, then returns a ‘1’.
*SRE
,
*SRE?
(service request enable) sets and queries the value of
the service request enable register.
*STB?
(status byte) queries the value of the status byte register
without erasing its contents.
Individual status registers can be set and queried using the commands
in the STATus subsystem of the language reference. A “status register”
is actually composed of five physical registers: a condition register, two
transition registers, an event enable register and an event register. You
can use the
:STATus
commands to:
• Check the analyzer hardware and firmware status.
Do this by querying the condition registers which continuously
monitor status. These registers represent the current state of the
analyzer. Bits in a condition register are updated in real time. When
the condition monitored by a particular bit becomes true, the bit is
set to 1. When the condition becomes false, the bit is reset to 0.
• Monitor a particular bit (condition), or bits.
Once you have enabled a bit, using the event enable register, the
analyzer will monitor that particular bit. If the bit becomes true in
the event register, it will stay set until the event register is cleared.
Querying the event register allows you to detect that this condition
occurred even if the condition no longer exists. The event register
can only be cleared by querying it or sending the
*CLS
command,
which clears all event registers.