3-7
3
If the register is not cleared, the event bits will remain set and they will not
generate another Service Request when the input again goes true.
STAT:QUES:COND?
‘reads the questionable inputs
3.3.4 Operation Registers
The 488.2 Operation Registers lets the user read device specific status condi-
tions and detect any changes in the device’s status. The Operation Registers
are similar to the Questionable Registers described in paragraph 3.3.3. In the
8099, the Operation Condition Register only reports the Local Lockout and
Remote interface states. The following commands demonstrate some possibili-
ties of the Operation Registers:
STAT:OPER:COND?
‘quires the Operation Condition Register
3.3.5 Output Queue
The Output Queue is used to output IEEE 488.2 and SCPI responses back to
the client. The Output Queue reports a ‘1’ in bit 4 of the Status Byte Register
when it contains a message(s) to be read by the bus controller. Reading the
contents of the Output Queue clears its summary bit. The Output Queue is read
by sending the 8099 a device_read message. If the Output Queue is not read
before sending another query, its contents will be lost and an error reported.
Good programming technique is to follow each query by reading the result.
Testing the Output Queue's summary bit before addressing the device to talk can
confuse the unit and lead to erroneous results. Do not use the Output Queue's
summary bit to determine when to read a response.
3.3.6 Status Byte Register
The 8099 generates a Service Request (SRQ) whenever any of the enabled
bits in the Status Byte Register become true and the 8099 is not processing
a device_read message. The Status Byte Register may be read with the de-
vice_readstb function or with the
*STB?
query. The device_readstb function
resets the RQS bit; the
*STB?
query does not change the bit. The Status Byte
Register is enabled by setting the corresponding bits in the Service Request
Enable Register with the
*SRE
command. e.g.
*SRE 160
‘Sets the SRE Register to 1010 0000 which
enables just the Event Status and Questionable
summary bits to generate SRQs.
