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25
I2C/SPI Triggering and Serial Decode
When Display Info is enabled, information about the selected signal sources
and their threshold voltage levels, as well as a waveform diagram, appears
on the screen.
SPI Triggering
To set up the oscilloscope to capture SPI signals, see
Signals"
After the oscilloscope has been set up to capture SPI signals, you can then
trigger on a data pattern that occurs at the start of a frame. The serial
data string can be specified to be from 4 to 32 bits long.
When you select the SPI trigger type and Display Info is enabled, a graphic
is displayed showing the current state of the frame signal, clock slope,
number of data bits, and data bit values.
1 Press [Trigger].
428
•
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.
The Timeout value can be set anywhere from 100 ns to 10 s.
When you press the Frame by softkey, the Display Info graphic changes
to show timeout selection or the current state of the chip select
signal.
b Press the Threshold softkey; then, turn the Entry knob to select the
chip select signal threshold voltage level.
The threshold voltage level is used in decoding, and it will become
the trigger level when the trigger type is set to the selected serial
decode slot.
on page 424.
Agilent InfiniiVision 4000 X-Series Oscilloscopes User's Guide
"Setup for SPI
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