I
2
S Triggering and Serial Decode 12
InfiniiVision 7000B Series Oscilloscopes User’s Guide 307
• Increasing value — triggers when the data value is increasing over time
and the specified value is met or exceeded. Use the Trigger softkey in
this menu to set the data value that must be reached. Use the Armed
softkey to set the value to which the data value must fall before the
trigger circuit is re- armed (ready to trigger again). The Armed
control reduces triggers due to noise.
This trigger condition is best understood when the digital data
transferred over the I
2
S bus is considered in terms of representing
an analog waveform. The figure below shows a plot of sample data
transmitted over an I
2
S bus for one channel. In this example, the
oscilloscope will trigger at the 2 points shown since there are two
instances in which the data increases from a value below (or at) the
“Armed” value to a value greater than (or equal to) the specified
“Trigger“ value.
If you select an “Armed” value that is equal to or greater than the
“Trigger” value, the “Trigger” value will be increased so that it is
always greater than the “Armed” value.
• Decreasing value — similar to the description above except the trigger
occurs on a descreasing data word value, and the “Armed” value is
the value to which the data must rise in order to re- arm the trigger.
5 Press the Base softkey and select a number base for entering data
values:
• Binary (2’s complement).
When Binary is selected, the Bits softkey appears. This softkey opens
the I
2
S Bits Menu for entering data values.
"Trigger" value
Trigger
Trigger
No trigger
"Armed" value
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