2470 High Voltage SourceMeter Instrument Reference Manual
Section 8: Triggering
2470-901-01 Rev. A /
May
2019
8-17
Input
The input mode is similar to the open-drain mode, except that a line in this mode is intended to be
used strictly as an input. When you place a line in input mode, the instrument automatically writes a
1
to the line to enable it to detect externally generated logic levels.
You can read an input line, but you cannot write to it. You also cannot change the logic level while the
line is in input mode. If you attempt to change the logic level of a line that is in input mode, an event
message is generated.
Trigger control modes
You can use the trigger control modes to synchronize instrument operation with the operation of other
instruments. These modes either detect or generate transitions in the state of the line, from high to
low (falling edge) or from low to high (rising edge). The input edge detection setting of the instrument
determines which type of transition is detected as an input trigger. Output triggers are typically
generated in the form of a pulse. The type of transition that occurs on the leading edge of the pulse is
determined by an output logic setting. The duration of the pulse is determined by a pulse width
setting.
You can use the trigger control modes with interactive triggering or with the trigger model. For more
information about the trigger modes and triggering, refer to
(on page 8-3).
Open-drain
When you set the instrument to trigger mode and place a line in open-drain mode, the line is
configured to be an open-drain signal with a 100 k
Ω
pull-up resistor. This makes the line compatible
with other instruments that use open-drain trigger signals, such as other Keithley Instruments
products that only support open-drain for its digital I/O. In this mode, you can use the line to detect
input triggers or generate output triggers, or both. To use this mode successfully, you must carefully
configure the input edge and output logic settings because both of these affect the initial state of the
trigger line. It is recommended that you reset the line before selecting and configuring this mode.
To use the line only as a trigger input:
1.
Reset the line.
2.
Set the input trigger edge detection type to falling, rising, or either.
The command that sets the detection type automatically sets the line high. This enables the line to
respond to and detect externally generated triggers.
Do not set the output trigger logic type to positive after setting the edge detection type. This sets the
line low, which will prevent the line from operating correctly as a trigger input.
