Keithley 2601B Reference Manual page 186

Series 2600B System SourceMeter® Instrument Reference Manual
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 Series 2600B 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 Series 2600B ignores the hardware value of the packet and generates a
trigger event. The Series 2600B 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 Series 2600B 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
0
0
0
0
1
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
Either edge
Falling edge
Rising edge
RisingA
RisingM
Synchronous
SynchronousA
SynchronousM
2600BS-901-01 Rev. B / May 2013
Hardware Pseudo line state Falling edge
value
0 0
1 0
0 1
1 1
- -
Input detected Output generated
Either Negative
Falling Negative
Rising Positive
Rising Positive
Rising Positive
Falling Positive
Falling Positive
Rising Negative
Rising edge
Detected Detected
- Detected
Detected -
Detected Detected
Detected Detected
Notes
Same as Rising
Same as Rising
Same as SynchronousA
Section 3: Functions and features
3-51