RIGOL  Chapter 5 Trigger 
5-34  MSO4000/DS4000 User’s Guide 
RS232 Trigger 
 
MSO4000/DS4000 can trigger on the start of a frame, error frame, check error or the 
specified data bit of the RS232 signal.  
 
RS232 bus is a serial communication mode used for the data transmission between 
PCs or between PC and terminal end. The RS232 serial protocol transmits a character 
by treating it as a frame of data consisting of 1 bit start bit, 5 to 8 bits data bits, 1 bit 
check bit and 1 to 2 bits stop bits. The format is as shown in the figure below.  
 
 
 
Figure 5-2 RS232 Bus Frame Format 
 
Press MENU (in the trigger control area (TRIGGER) at the front panel)  Type, turn 
the multi-function knob   to select “RS232” and press the knob. You can also press 
Type continuously to switch to “RS232” trigger.  
At this point, the trigger setting information (include the trigger type, trigger source 
and trigger level/threshold level, as shown in the figure below) is displayed at the 
upper-right side of the screen and changes with the trigger setting.  
 
 
Set the RS232 trigger: 
 
1.  Specify the source and adjust the trigger level/threshold level 
1)  Press Source to select CH1 to CH4 or D0 to D15 (please refer to “Trigger 
Source”). The source currently selected is displayed at the upper-right side 
of the screen. 
 
Note: Channels that are turned off can also be selected as the trigger 
source. 
 
2)  Turn TRIGGER 
  LEVEL to adjust the trigger level (when the source is 
CH1 to CH4) or threshold level (when the source is D0 to D15) (please refer 
Start Bit 
Data Bits 
Check Bit 
Stop Bits 
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