Keithley 2657A User Manual

Section 3: Functions and features Model 2657A High Power System SourceMeter® Instrument Reference Manual
3-50 2657A-901-01 Rev. B/December 2012
Understanding hardware value and pseudo line state
LAN triggering is similar to hardware synchronization except that LXI trigger packets are used instead
of hardware signals. A bit in the LXI trigger packet called the hardware value simulates the state of a
hardware trigger line. The Model 2657A stores the hardware value of the last LXI trigger packet that
was sent or received as the pseudo line state.
The stateless event flag is a bit in the LXI trigger packet that indicates if the hardware value should be
ignored. If it is set, the Model 2657A ignores the hardware value of the packet and generates a trigger
event. The Model 2657A always sets the stateless flag for outgoing LXI trigger packets. If the
stateless event flag is not set, the hardware value indicates the state of the signal.
Changes in the hardware value of consecutive LXI trigger packets are interpreted as edge transitions.
Edge transitions generate trigger events. If the hardware value does not change between successive
LXI trigger packets, the Model 2657A assumes an edge transition was missed and generates a
trigger event. The following table illustrates edge detection in LAN triggering.
Instruments that are compliant to LXI versions before 1.2 always process the hardware value.
Instruments compliant to LXI version 1.2 and later are required to ignore the hardware value when the
stateless event flag is set.
LXI trigger edge detection
Stateless event
flag
Hardware
value
Pseudo line state Falling edge Rising edge
0 0 0 Detected Detected
0 1 0 - Detected
0 0 1 Detected -
0 1 1 Detected Detected
1 - - Detected Detected
Set the LAN trigger mode to configure the edge detection method in incoming LXI trigger packets.
The mode that is selected also determines the hardware value in outgoing LXI trigger packets. The
following table lists the LAN trigger modes.
LAN trigger modes
Trigger mode Input detected Output generated Notes
Either edge Either Negative
Falling edge Falling Negative
Rising edge Rising Positive
RisingA Rising Positive Same as Rising
RisingM Rising Positive Same as Rising
Synchronous Falling Positive Same as SynchronousA
SynchronousA Falling Positive
SynchronousM Rising Negative
NOTE

Keithley 2657A Specifications

General

Brand	Keithley
Model	2657A
Category	Measuring Instruments
Language	English