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C/SPI Triggering and Serial Decode 11
InfiniiVision 7000B Series Oscilloscopes User’s Guide 295
SPI Triggering
To set up the oscilloscope to capture SPI signals, see “Setup for SPI
Signals” on page 292.
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, a graphic will be displayed showing
the current state of the frame signal, clock slope, number of data bits, and
data bit values. Press the Signals softkey in the Settings Menu to see the
current source channels for the clock, data, and frame signals.
1 Press [Trigger]; then, select the SPI trigger type.
2 Repeatedly press and release the Trigger: softkey or rotate the Entry
knob to select the trigger condition.
3 Press the #Bits softkey, and turn the Entry knob to set the number of
bits (#Bits) in the serial data string. The number of bits in the string
can be set anywhere from 4 bits to 32 bits. The data values for the
serial string are displayed in the Data string in the waveform area.
4 Turn the Entry knob to select a specific data bit in the serial string as
shown in the Bit softkey.
As you rotate the Entry knob, the bit is highlighted in the Data string
shown in the waveform area.
5 Press the 0 1 X softkey to set the bit selected in the Bit softkey to
0 (low), 1 (high), or X (don't care).
Repeat the last two steps to assign values for all bits.
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