User Manual

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15.3 UART/RS232 Serial Decode
The following order of operations should be followed to ensure that the trigger and decode
functions are set correctly:
• Setup for UART/RS232 Signals
• UART/RS232 Decode
Setup for UART Signals
To set up the oscilloscope to capture UART signals:
1. Press the Decode button to turn on 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 UART with the Universal Knob and push it to confirm.
4. Press the Signal softkey to enter the UART/RS232 SIGNAL menu.
Figure 115 - UART SIGNAL menu
5. For both the RX and TX signals:
a. Connect an oscilloscope channel to the appropriate signal on the device under test.
b. Press the RX or TX softkeys to select the channel for the signal.
c. Press the corresponding Threshold softkey and turn the Universal Knob to select the
signal's 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.
The threshold can be set from -4.5 to 4.5 volts.
d. Press Bit Order softkey to select between least significant bit (LSB) and most significant
bit (MSB) order.
6. Press the softkey to return to the DECODE menu.
7. Press the Configure softkey to open the BUS CONFIG menu. Set the following parameters.
Figure 116 - BUS CONFIG menu
 Baud: Press the Baud softkey, then press the Universal Knob and select a baud rate to
match the signal in your device under test. If the desired baud rate is not listed, select
Custom on the Baud softkey and press the Custom softkey. Turn the Universal Knob to
set the desired baud rate. The maximum baud rate is 50,000,000.
 Parity Check: Choose Odd, Even, or None, based on your device under test.
 Stop Bit: Set the number of stop bits in the UART/RS232 words to match your device
under test.