User`s guide

4 Triggering
154 InfiniiVision Oscilloscopes User’s Guide
• If the framing signal is set to CS (or ~CS), the first clock edge as defined, rising or
falling, seen after the CS (or ~CS) signal transitions from low to high (or high to
low) is the first clock in the serial stream.
Chip Select — Press the CS or ~CS softkey or turn the Entry knob to select the
channel that is connected to the SPI frame line. The label (~CS or CS) for the
source channel is automatically set. The data pattern and the clock transition must
occur during the time when the framing signal is valid. The framing signal must be
valid for the entire data pattern.
As you press the CS or ~CS softkey (or rotate the Entry knob), the CS or ~CS label
for the source channel is automatically set and the channel you select is shown in
the upper-right corner of the display next to “SPI”. When you press the Frame by
softkey, the graphic shown on the previous page changes to show timeout
selection or the current state of the chip select signal.
If you have connected one of the oscilloscope’s analog source channels to the Chip
Select signal: Adjust the trigger level for the selected analog channel to the middle
of the waveform by turning the Trigger Level knob.
If you have connected one of the oscilloscope’s digital source channels to the Chip
Select signal (this applies to MSO model oscilloscopes only): Press the [D15-D0]
key and select Thresholds to set an appropriate threshold level for digital channels.
• If the framing signal is set to Timeout, the oscilloscope generates it’s own internal
framing signal after it sees inactivity on the serial clock line.
Clock Timeout — Select Clock Timeout in the Frame by softkey, then select the
Timeout softkey and turn the Entry knob to set the minimum time that the Clock
signal must be idle (not transitioning) before the oscilloscope will search for the
Data pattern on which to trigger. When you press the Frame by softkey, the graphic
shown on the previous page changes to show timeout selection or the current
state of the chip select signal.
The Timeout value can be set anywhere from 100 ns to 10 s.
10 Press the up-arrow softkey to return to the previous menu.