Chapter 4 Remote Interface Reference
The SCPI Status Registers
96
Using *STB? to Read the Status Byte
The
*STB?
(Status Byte query) co mmand is similar to a serial poll but it is
processed like any other instrument c ommand. The
*STB?
command returns
the same result as a serial poll but the “request service” bit (bit 6) is not cleared.
The
*STB?
comm and is not handled automatically by the IEEE-488 bus
interface hardware and will be executed only after previous commands have
completed. Polling is not possible using the
*STB?
comm and. E xecuting the
*STB?
comm and does not clear the Status Byte summary register.
Using the Message Available Bit (MAV)
You can use the Status Byte “messag e available ” bit (bit 4) to determine when
data is available to read into your bus controller. The power supply
subsequently clears bit 4
only
after all messages have been read from the
output buffer.
To Interrupt Your Bus Controller Using SRQ
1
Send a device clear message to clear the power supply’s output buffer (e.g.,
CLEAR 705).
2
Clear the event registers with the *CLS (clear status) command.
3
Set up the enable register masks. Execute the *ESE command to set up the
Standard Event register and the
*SRE command for the Status Byte.
4
Send the *OPC? (operation complete query) command and enter the result to
ensure synchronization.
5
Enable your bus controller’s IEEE-488 SRQ interrupt.
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