Keithley 2100 User Manual page 135

Model 2100 6 1/2-Digit Resolution Digital Multimeter User's Manual
On the other hand, there are some conditions that users have to note.
The following conditions will clear the summary register:
The following conditions will clear the enable register:
NOTE
How to use SRQ (Service Request) and Serial Poll
You have to set the bus controller to repond to the IEEE-488 SRQ and interrupt to use this
capability. Use the status byte enable register (SRE) to select the low-level IEEE-488 SRQ signal
set by summary bits. As the status byte bit 6 is set, an IEEE-488 SRQ interrupt message will be
sent automatically to the bus controller which may poll the instruments on the bus to identify which
one requested service. To read the status byte which is using an IEEE-488 serial poll or to read the
event register, whose summary bit is cauing the service request, will clear the request service.
Send the IEEE-488 serial poll message to read the status byte summary register. And to query the
summary register will return a
the bits set in the register. And serial poll will clear the "request service bit" automatically
in the status byte summary register, but no other bits are affected, for example, to perform
a serial poll will not affect the instrument throughput.
NOTE
Read the Status Byte by using *STB?
The *STB? command (status byte query) is like a serial poll except it acts similar to any other
instrument command. This command returns the same result as an IEEE-488 serial poll except
that the "request service bit 6" is not cleared if a serial poll has occurred. And the IEEE-488 bus
interface hardware cannot automatically handle the *STB? command. It will work only after
previous commands have completed, and it is impossible to poll by using the *STB? command.
Moreover, to use this command does not clear the status byte summary register.
Procedures of Interrupting the Bus Controller by Using SRQ
Procedures to Determine When a Command Sequence is Completed.
2100-900-01 Rev. D / September 2011
• Users execute a *CLS (clear status) command.
• To query the standard event and questionable data registers will clear only the separate bits
in the summary register.
• Users turn on the power, and have set the DMM previously by using the *PSC 1 command.
• Users execute a *SRE 0 command.
If you have set the DMM previously by using *PSC 0, the status byte enable register will
not be cleared at power-on.
The synchronization between the bus controller program and the instrument is not able to
be ensured by the IEEE-488.2 standard. So you can apply the *OPC? command to
ensure that commands sent to the instrument previously have completed. And to
execute a serial poll before applying *RST, *CLS or other commands have completed
can allow pervious conditions to be reported.
• Send a bus device clear message.
• Clear the event register by using the *CLS command.
• Set the *ESE and *SRE commands to enable masks.
• Send the *OPC? command and enter the result to enable synchronization.
• Enable the bus controller's IEEE-488 SRQ interrupt.
• Clear the DMMís output buffer by sending a device clear message.
• Clear the event registers by using *CLS command.
Return to
decimal value corresponding to the binary-weighted sum of
Section Topics
Appendix B: Remote Interface Reference
B-23