2-29
IM 701450-51E
CAN Bus Signal Analysis Function
2
Stuff Bit Computation
You can specify whether to perform stuff bit computation in parallel with analysis.
OFF
Do not perform stuff bit computation.
ON
Perform stuff bit computation.
• The stuff bit computation result is displayed as the Math1 waveform.
• Scaling is fixed to
±
2.0.
Stuff bit:
High level (+1.0)
Other than stuff bit: Low level (0.0)
Notes When Executing Stuff Bit Computation
If you change Select Record in the History menu while the stuff bit waveform is
displayed, the changed history waveforms are displayed on channels other than the stuff
bit computation waveform (Math1), but Math1 is cleared. To update the stuff bit
computation waveform to the changed history waveform, you must execute analysis
again.
Note
Stuff bit computation cannot be performed for the following record lengths.
•
16 MW memory model (701460 and 701480)
When Interleave Mode is ON:
8 MW
When Interleave Mode is OFF: 4 MW
•
4 MW memory model (701450 and 701470)
4 MW
In the above case, if you execute analysis with the stuff bit setting turned ON, the message
“Computation cannot be carried out at the current record length.” (error code: 851) appears.
Stuff Bit
The CAN Bus is designed to prevent burst errors by disallowing 6 continuous bits or
more from having the same level. On the sending side, if 5 or more continuous bits
between the Start of Frame and CRC fields are at the same level, CAN inserts a bit(stuff
bit) having the opposite logical value of the 5 previous bits for the next bit (6th bit). On
the receiving side, this bit is deleted prior to receiving the signal.
The DL7440/DL7480 lets you extract stuff bits from the CAN Bus signal waveform and
display them as a Math waveform (Math1).
1 2 3 4 5
6
1 2 3 4 5
6
Low
High
Other: Low level
Stuff bit
Signal flowing on
the bus (CH1)
Stuff bit computation
waveform (Math1)
Stuff bit: High level
2.5 Analyzing/Searching Data
