Keithley 2450 Reference Manual page 259

Section 3: Functions and features
Understanding hardware value and pseudo line state
LAN triggering and hardware synchronization are similar, except that LAN triggering uses LXI trigger
packets 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 2450 stores the hardware value as the
pseudo-line state. Only the state of the last LXI trigger packet that was sent or received is stored.
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 2450 ignores the hardware value of the packet and generates a trigger
event. The Model 2450 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.
The instrument interprets changes in the hardware value of consecutive LXI trigger packets as edge
transitions. Edge transitions generate trigger events. If the hardware value does not change between
successive LXI trigger packets, the Model 2450 assumes an edge transition was missed and
generates a trigger event. The following table shows edge detection in LAN triggering.
LXI trigger edge detection
Stateless event
flag
0
0
0
0
1
You can set the LAN trigger edge detection method in incoming LXI trigger packets. The edge that is
selected also determines the hardware value in outgoing LXI trigger packets. The following table lists
the LAN trigger edges.
Trigger mode
Either edge
Falling edge
Rising edge
The example below illustrates how to configure the LAN trigger edge.
-- Set LAN trigger 2 to detect the falling edge.
trigger.lanin[2].edge = trigger.EDGE_FALLING
LAN trigger objects generate LXI trigger events, which are LAN0 to LAN7 (zero based). To specify
the LAN trigger event in a command, use trigger.EVENT_LANN, where N is 1 to 8.
trigger.EVENT_LAN1 corresponds to LXI trigger event LAN0 and trigger.EVENT_LAN8
corresponds to LXI trigger event LAN7.
Generate LXI trigger packets
You can configure the Model 2450 to output an LXI trigger packet to other LXI instruments.
To generate LXI trigger packets:
1. Call the trigger.lanout[N].connect() function.
2. Select the event that triggers the outgoing LXI trigger packet by assigning the specific event to
the LAN stimulus input.
Make sure to use the same LXI domain on both the Model 2450 instrument and the other instrument.
If the Model 2450 has a different LXI domain than the instrument at the other end of the trigger
connection, the LXI trigger packets are ignored by both instruments.
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Model 2450 Interactive SourceMeter® Instrument Reference Manual
Hardware Pseudo-line
value state
0 0
1 0
0 1
1 1
- -
Input detected Output generated
Either Negative
Falling Negative
Rising Positive
Falling edge Rising edge
Detected Detected
- Detected
Detected -
Detected Detected
Detected Detected
2450-901-01 Rev. B/September 2013