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Chapter 4 Remote Interface Reference
The SCPI Status Registers
107
4
The Status Byte Summary register is cleared when:
• You execute the
*CLS
(clear status) command.
• Querying the Standard Event register (
*ESR?
command) will clear only bit
5 in the Status Byte summary register.
For example, 24 (8 + 16) is returned when you have queried the status of the
Status Byte register, QUES and MAV conditions have occurred.
The Status Byte Enable register (Request Service) is cleared when:
• You execute the
*SRE 0
command.
• You turn on the power and have previously configured the power supply
using the
*PSC 1
command.
• The enable register will not be cleared at power-on if you have previously
configured the power supply using
*PSC 0
.
Using Service Request (SRQ) and Serial POLL
You must configure your bus controller to respond to the IEEE-488 service
request (SRQ) interrupt to use this capability. Use the Status Byte enable
register (
*SRE
command) to select which summary bits will set the low-level
IEEE-488 service request signal. When bit 6 (request service) is set in the Status
Byte, an IEEE-488 service request interrupt message is automatically sent to
the bus controller. The bus controller may then poll the instruments on the bus
to identify which one requested service (the instrument with bit 6 set in its
Status Byte).
The request service bit is cleared only by reading the Status Byte using an
IEEE-488 serial poll or by reading the event register whose summary bit is
causing the service request.
To read the Status Byte summary register, send the IEEE-488 serial poll
message. Querying the summary register will return a decimal value which
corresponds to the binary-weighted sum of the bits set in the register. Serial
poll will automatically clear the “request service” bit in the Status Byte
summary register. No other bits are affected. Performing a serial poll will not
affect instrument throughput.
Caution The IEEE-488 standard does not ensure synchronization between your bus controller
program and the instrument. Use the *OPC? command to guarantee that commands
previously sent to the instrument have completed. Executing a serial poll before a
*RST, *CLS, or other commands have completed can cause previous conditions
to be reported.