Event Registers; Condition Registers; Queues; Output Queue - Tektronix Keithley 2281 Series Reference Manual

Appendix D: Status model

Event registers

Each status register set has an event register. When an event occurs, the appropriate event register
bit sets to 1. The bit remains latched to 1 until the register is reset. Reading an event register clears
the bits of that register. The *CLS command resets all the event registers.
The commands to read the event registers are described in
Event enable registers
Each status register has an enable register. Each event register bit is logically ANDed (&) to a
corresponding enable bit of an enable register. Therefore, when an event bit is set and the
corresponding enable bit is set (as programmed by the user), the output (summary) of the register will
set to 1.
The commands to program and read the event enable registers are described in
(on page 7-147).

Condition registers

The 2281S has the following condition registers:
Operation Instrument Summary Condition Register
Questionable Instrument Summary Condition Register
Measurement Instrument Summary Condition Register
A condition register is a real-time, read-only register that constantly updates to reflect the present
operating conditions of the instrument. For example, while the 2281S is in the idle state, bit B10 (idle)
of the Operation Instrument Summary Condition Register will be set. When the instrument is taken
out of the idle state, bit B10 clears.

Queues

The instrument includes an Output Queue and an Error Queue. The Output Queue holds messages
from readings and responses. The Error Queue holds error messages from the event log. Both are
first-in, first-out (FIFO) registers.

Output queue

The output queue holds response messages to query and print the commands.
When data is placed in the output queue, the message available (MAV) bit in the Status Byte Register
is set. The bit is cleared when the output queue is empty.
D-20
Model 2281S-20-6 DC Power Supply and Battery Simulator Reference Manual
STATus subsystem (on page 7-147).
STATus subsystem
077114601 / March 2019