Keysight E8402A, E8404A C-Size Mainframes User and Service Guide 105STATus Subsystem Programming the Enhanced MonitorSTATus SubsystemSCPI uses four status groups - the Status Byte, the Standard Event status group,the Operation status group, and the Questionable Data status group. The STATussubsystem controls those command (and queries) that affect the OPERationstatus group and the QUEStionable status group.The OPERation status group provides information about the state of themonitoring systems in an instrument. The QUEStionable data status groupprovides information about the quality of instrument output and monitoring data.Each status group consists of a condition register, transition filters, eventregister, and enable register. The enable register values are stored in non-volatilememory with the SYSTem:NVSave command and restored at power-on.The CONDition register continuously monitors the hardware and firmware statusof the instrument. There is no latching or buffering for this register; it is updatedin real time. Condition registers are read-only.The EVENt register latches transition events from the condition register asspecified by the transition filter. Only the positive transition filter is active in themodule, this means that a transition event will occur when a condition makes atransition from a low to a high state 1. Bits in the event register are latched, andonce set, they remain set until cleared by a STATus:OPERation:EVENt? query or*CLS (clear status). There is no buffering; so while an event bit is set, subsequentevents corresponding to that bit are ignored. Event registers are read only. Eventsare queried in order to determine if transitions have occurred since the last query.They do not indicate the current state (condition) of a particular event. Nor dothey indicate how many times a transition has occurred.The ENABle register specifies which bits in the event register can generate asummary bit. The instrument logically ANDs corresponding bits in the event andenable registers, and ORs all the resulting bits to obtain a summary bit. Summarybits are, in turn, recorded in another register. The OPERation and QUEStionablestatus summary bits are recorded in the Status Byte. Enable registers areread-write. Enable registers are not affected by *CLS (Clear status). Queryingenable registers does not affect them.Figure 0-1 shows a simplified register diagram for the status subsystem.1 The only exception is the STATus:QUEStionable:VOLTage register which is set with theSTATus:QUESTionable:VOLTage:PTR command.
