Serial Bus Decoding & Triggering, Search & Navigation, and Segmented Acquisition Labs
4
4000 X-Series Oscilloscopes Advanced Training Guide
81
You should see on your scope’s display what appears to be an un-triggered display
of two digital signals similar to
. Your scope is actually triggering on
random rising edges of channel-1, which is the scope’s default trigger condition.
But these signals are too complex to establish a unique trigger point using simple
edge triggering. The signal being captured by channel-1 is an I
2
C serial clock
signal (SCL), and the signal being captured by channel-2 is an I
2
C serial data
signal (SDA). Let’s first set up the scope to intelligently decode this data stream
based on the I
2
C protocol, and then we will establish a more unique trigger point
using I
2
C triggering.
12
Press the
[Serial]
front key.
13
Tap the
Mode
softkey; then select the
I
2
C
serial decode mode.
14
Tap the
Signals
softkey and verity that
SCL
is defined as channel-1, and that
SDA
is defined as channel-2 (default conditions). Set each Threshold level to ~1.3 V
if not set already.
15
Press the (Back) front panel button (above power switch) to return to the
previous menu.
16
Tap the
Addr Size
softkey and verify that
7 Bit
is selected.
17
Tap the
Lister
softkey; then select
Window
and tap
Half-Screen
to show a list of
Serial 1 (I2C).
Figure 50
Capturing I
2
C clock and data while triggering on an edge of the clock (channel-1).
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