User Manual

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15 Serial Bus Decoding (DC2540C)
The oscilloscope provides I2C, SPI, UART/RS232, CAN and LIN serial trigger and decode. This
chapter shows how to set and use these types of serial decoding. Serial bus decoding requires
the license to be installed. To purchase a license key, please fill out the license request form or
visit the 2540C Series accessories page.
15.1 I2C Serial Decode
Setup for I2C Signals
I2C (Inter-IC bus) signals setup consists of connecting two analog channels to the serial data (SDA)
line and the serial clock (SCL) line and specifying the input signal threshold voltage levels.
To set up the oscilloscope to capture I2C signals:
1. Press the Decode button to display the Decode menu.
2. Press the Decode softkey and select the desired slot: Decode 1 or Decode 2.
3. Press the Protocol softkey and select I2C with the Universal Knob and push the Universal
Knob to confirm.
4. Press the Signal softkey to enter the I2C SIGNAL menu.
Figure 106: I2C SIGNAL menu
5. For both the SCL (serial clock) and SDA (serial data) signals:
a. Connect an oscilloscope analog or digital channel to the signal on the device under test.
b. Press the SCL or SDA softkey and turn the Universal Knob to select the channel for that
signal.
c. Press the corresponding Threshold softkey and turn the Universal Knob to set the 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.
 Data must be stable during the entire high clock cycle or it will be interpreted as a start or
stop condition (data transitioning while the clock is high).
I2C Serial Decode
To set up I2C serial decode:
1. Press the Decode button to display the Decode menu.
Figure 107: I2C decode menu