Using *STB? to Read the Status Byte
The *STB? (status byte query) command is similar to a serial poll except
it is processed like any other instrument command. The *STB? command
returns the same result as an
IEEE-488 serial poll except that the
“request service” bit (bit 6) is not cleared if a serial poll has occurred.
The *STB? command is not handled automatically by the
IEEE-488 bus
interface hardware and the command will be executed only after previous
commands have completed. Polling is not possible using the *STB?
command. Using the *STB? command does not clear the status byte
summary register.
To Interrupt Your Bus Controller Using SRQ
• Send a bus device clear message.
• Clear the event registers with the *CLS (clear status) command.
• Set the *ESE (standard event register) and *SRE (status byte register)
enable masks.
• Send the *OPC? (operation complete query) command and enter the
result to assure synchronization.
• Enable your bus controller’s
IEEE-488 SRQ interrupt.
To Determine When a Command Sequence is Completed
Either:
• Send the *OPC? (operation complete query) command and enter the
result to assure synchronization.
Or, to prevent holding the interface bus for commands that take longer
to execute (such as CALibrate commands), :
• Send a device clear message to clear the meter’s output buffer.
• Clear the event registers with the *CLS (clear status) command.
• Enable “operation complete” using the *ESE 1 command (standard
event register).
• Send your programming command string, and place the *OPC
(operation complete) command as the last command.
• Use a serial poll to check to see when bit 5 (standard event) is set in the
status byte summary register. You could also configure the meter for an
SRQ interrupt by sending *SRE 32 (status byte enable register, bit 5).
4
Chapter 4 Remote Interface Reference
The SCPI Status Model
163
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