Keithley SourceMeter 2600 Series Reference Manual page 530

D-2 Status Model
Overview
The SourceMeter provides a number of status registers and queues allowing the
operator to monitor and manipulate the various instrument events. The status
model is shown in
the Status Byte Register. This register can be read by the user's test program to
determine if a service request (SRQ) has occurred, and what event caused it.
Status byte and SRQ
The Status Byte Register receives the summary bits of five status register sets
and two queues. The register sets and queues monitor the various instrument
events. When an enabled event occurs, it sets a summary bit in the Status Byte
Register. When a summary bit of the Status Byte is set and its corresponding
enable bit is set (as programmed by the user), the RQS/MSS bit will set to indicate
that an SRQ has occurred, and the GPIB SRQ line will be asserted.
Status register sets
A typical status register set is made up of a condition register, an event register
and an event enable register (many also have negative and positive transition reg-
isters). A condition register is a read-only register that constantly updates to
reflect the present operating conditions of the instrument.
When an event occurs, the appropriate event register bit sets to 1. The bit remains
latched to 1 until the register is reset. When an event register bit is set and its
corresponding enable bit is set (as programmed by the user), the output
(summary) of the register will set to 1. This in turn sets another bit in a lower-level
register, and ultimately sets the summary bit of the Status Byte Register.
Queues
The SourceMeter uses an Output Queue and an Error Queue. The response
messages, such as requested readings, are placed in the Output Queue. As
various programming errors and status messages occur, they are placed in the
Error Queue. When a queue contains data, it sets the appropriate summary bit of
the Status Byte Register (EAV for the Error Queue; MAV for the Output Queue).
2600S-901-01 Rev. A / May 2006
Series 2600 System SourceMeters Reference Manual
Figure D-1 through Figure
Return to Appendix D topics
D-5. The heart of the status model is