2-4
IM 701450-51E
Differential Probe Connection Method
CAN has two standards, High speed CAN (ISO11898) and Low speed CAN (ISO11519-
2).
0
1
2
3
4
5
0
1
CAN_High
CAN_Low
Node n
(Max:30)
Node 1
High speed CAN (ISO11898)
CAN_High
CAN_Low
0
1
2
3
4
5
1
0
2.2 k
Ω
2.2 k
Ω
CAN_High
CAN_Low
Node n
(Max:20)
Node 1
Low speed CAN (ISO11519-2)
CAN_Low
CAN_High
120
Ω
120
Ω
Logical
value
CAN Bus physical signaling
CAN Bus physical signaling
Bus le
vel (V)
Bus le
vel (V)
Recessive
Dominant
Recessive
Recessive
Logical
value
Recessive
Dominant
In the figure above, the bus level is determined for both High and Low speed CAN
according to the difference of potential between the CAN_High and CAN_Low busses.
The bus has two levels, dominant and recessive, and the signal must be at one of those
levels.
The instrument normally handles the dominant logical value as 0 and the recessive
logical value as 1, but depending on how the differential probe is set up, you can select
whether to display the dominant or recessive as the higher voltage level.
Connecting the Differential Probe
When the Recessive Voltage Level is Displayed as Higher Than the Dominant
Voltage Level
(Vdiff: CAN_L–CAN_H
1
)
Recessive (Logical value: 1)
Dominant (Logical value: 0)
• For a Two Wire System (Differential)
Connect the differential probe negative (–) to CAN_High, and the probe positive (+) to
CAN_Low.
• For a One Wire System (Single-Ended)
Connect the differential probe negative (–) to CAN_High, and probe positive (+) to
GND (ground potential).
When the Recessive Voltage Level is Displayed as Less Than the Dominant
Voltage Level
(Vdiff: CAN_H–CAN_L
1
)
Dominant (Logical value: 0)
Recessive (Logical value: 1)
• For a Two Wire System (Differential)
Connect the differential probe negative (–) to CAN_Low, and the probe positive (+) to
CAN_High.
• For a One Wire System (Single-Ended)
2
Connect the differential probe negative (–) to GND (ground potential), and the probe
positive (+) to CAN_High.
1 These items are set in the CAN Setup dialog box (see page 2-5) and the Analyze Setup
dialog box (see page 2-20). Select CAN_L-CAN_H or CAN_H-CAN_L depending on how the
probe is connected. For details, see the explanation for each dialog box.
2 In this case the passive probe (model 700988) can be connected to CAN_High
2.3 Connecting the Probe