The PWX has two mandatory SCPI standard registers, STATus:OPERation and STATus:QUEStionable, in addition to the IEEE488.2 standard registers.
All SCPI registers have standard event/filter architecture, employing CONDition, EVENt, ENABle, and optionally PTRansition and NTRansition. CONDition and EVENt are read-only registers working as status indicators, and ENABle, PTRansition and NTRansition are read-write registers working as event and summary filters.
The STATus:OPERation register records events or signals that occur during normal operation.
For example, to check if the PWX is being regulated in CV state, check the CV bit (bit 8) on the STATus:OPERation register.
:STATus:OPERation? 'Check whether the CV bit is set
The STATus:QUEStionable register records events or signals that indicate abnormal operation.
To check if the protection function is working, check the OV bit (bit 0) on the STATus: QUEStionable register.
:STATus:QUEStionable? 'Check whether the OV bit is set
PON (Power ON) bit
The PON bit (bit 7) in the event status register is set whenever the PWX is turned on. The most common use for the PON bit is to generate an SRQ at power-on to keep track of unexpected loss of power or power line failure. To do this, follow the steps shown below.
1. Set *PSC (Power-on Status Clear) to 0 (or OFF).
Enable the backup function of the event status enable register and service request enable register (*PSC 0).
2. Set the PON bit (bit 7) of the event status enable register.
Permit the transmission of a power-on event to the upper layer (*ESE 128).
3. Set the ESB bit (bit 5) of the status byte enable register.
Permit the generation of an SRQ caused by a standard event (*SRE 32).
*PSC 0;*ESE 128;*SRE 32
When using the RS232C interface, the PON bit cannot be assigned to the service request, because SRQs are not generated.
Though the SRQ feature itself is provided by communication protocol on the USB interface or LAN (VXI-11/ HiSLIP) interface, a Connection Lost error in the VISA I/O session occurs immediately before the power-on event. It may be difficult to handle PON events when using the USB interface.