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6482-901-01 Rev. A / August 2012
Section 13: Status Structure
Model 6482 Dual-Channel Picoammeter / Voltage Source Reference Manual
Overview
Each Keithley Instruments Model 6482 provides a number of status registers and queues that are
collectively referred to as the "status model." Through manipulation and monitoring of these
registers and queues, you can view and control various instrument events. You can include
commands in your test program that can determine if a service request (SRQ) event has occurred
and the cause of the event.
The status structure is shown in
. The center of the status structure is the status byte
register; all status model registers and queues flow into the Status Byte Register.
Status byte and SRQ
The status byte register receives the summary bits of four 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 request for service/
master summary status (RQS/MSS) bit will set to indicate that an SRQ has occurred.
Status register sets
A typical status register set is made up of a condition register, an event register, and an event
enable register. 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) bit of the register will set to 1, which then sets
the summary bit of the status byte register.
Queues
The Model 6482 uses an output queue and an error queue. The response messages to query
commands 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.
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