Agilent Technologies 54621A, 54621D, 24A, 42A, 22A, 41A Ack Data Stop Start Address R/W Condition

Triggering the Oscilloscope

To use I2C triggering

3Connect an oscilloscope channel to the SDA (serial data) line in the circuit under test, then set the SDA data channel softkey to that channel.

As you press the SDA softkey (or rotate the Entry knob on mixed-signal oscilloscopes), the SDA 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 "I2C".

Adjust the trigger level for the selected analog channel by turning the Trigger Level knob. For the mixed-signal oscilloscope, select Threshold in the D7 Thru D0 or D15 Thru D8 menu to set the level for digital channels assigned to the clock and data lines. The value of the trigger level or digital threshold is displayed in the upper-right corner of the display.

Data needs to be stable during the whole high clock cycle or it will be interpreted as a start or stop condition (data transitioning while the clock is high).

4Press the Trigger: softkey to select one of the following I2C trigger conditions:

Start Condition: the oscilloscope triggers when SDA data transitions from high to low while the SCL clock is high. For triggering purposes (including frame triggers), a restart is treated as a start condition.

Stop Condition: the oscilloscope triggers when data (SDA) transitions from low to high while the clock (SCL) is high.

SDA

SCL

	Ack	Data	Ack	Stop
Start Address R/W
Condition				Condition

Missing Acknowledge: the oscilloscope triggers when SDA data is high during any Ack SCL clock bit.

Restart: the oscilloscope triggers when another start condition occurs before a stop condition.

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