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Remote Operation76
The first four bits (0 to 3) in the register tell whether or not a particular output has a fault. If there is a fault in one of the
outputs, then the corresponding FAU bit will be set. Thus if output 1 has a fault, then FAU 1 will be set. In models with
only three outputs, FAU 4 will always be zero and in two output models, FAU 3 and FAU 4 will always be zero.
The RDY bit is set when processing is complete and is cleared when the supply is processing commands.
The ERR bit is set when a programming or hardware error occurs and is cleared when the error query (ERR?) is received.
The error annunciator on the front panel informs the user when this bit is set or cleared.
The RQS bit is set when the power supply generates a service request and cleared after a serial poll is done (see the
following paragraph, Service Request Generation).
The PON bit is set at power on and cleared when a CLR command is sent.
Service Request Generation
When operating your supply, you may want it to request service every time a fault or a programming error condition
occurs. To do this you send a service request (SRQ) command. When the condition is true, the power supply responds by
setting the RQS bit in the serial poll register, setting the SRQ annunciator on the front panel, and issuing an SRQ over the
HP-IB.
The 662xA supplies can generate a service request for any of the following reasons: (refer to Table 5-7).
• An Output Fault. If there is a fault on one or more of the output channels and you previously sent the SRQ 1 or
SRQ 3 command (see Service Request Enable/Disable information below), then an SRQ will be generated.
• An Error. If there is an error (see Tables 5-8) and you previously sent the SRQ 2 or SRQ 3 command, (see Service
Request Enable/Disable information below), then the supply will generate a service request.
• Power-on. At power-on, the PON bit of the serial poll register is set but the supply will only generate an SRQ if you
previously sent a PON 1 command.
• Input Line Voltage Dropout. Same as power-on condition.
To find out the nature of the service request, you must do a serial poll. This will isolate the output that generated the
request by checking which of the FAU bits are set in the case of a fault, or checking to see if the error bit is set in the case
of an error. If the SRQ on faults was set, then send the fault query.
FAULT? 2 (using output 2 as an example)
and address the supply to talk if you want to find out which of the conditions you unmasked in Figure 5-3 are true. For
example if the supply was in overvoltage and that condition was unmasked then the response from the fault query will be
''8" (see Table 5-5).
NOTE When you query the fault, the fault register is cleared. Performing a serial poll will reset the PQS bit but
will not clear the fault register.
If the SRQ on error was set, then you can send the error query ERR? and address the supply to talk. The response will
identify the error by its code (see Table 5-8).