Keithley 6430, Instruction Manual

Page: 280 / 558

14-2 Status Structure
Overview
The SourceMeter provides a series of status registers and queues allowing the operator to
monitor and manipulate the various instrument events. The status structure is shown in Figure
14-1. The heart of the status structure is 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 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 Sta-
tus 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.
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 re fl ect 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, which in
turn sets the summary bit of the Status Byte Register.
Queues
The SourceMeter 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.