Campbell Hausfeld SDM-CAN - Manual (Page 12)

SDM-CAN CAN-Bus Interface User Guide
2.2 Internal Jumper Settings
The SDM-CAN interface is fitted with a number of jumpers which configure the
connection to the CAN network.
Prior to setting these jumpers you need to give some consideration on how best to
connect the SDM-CAN interface to the network:
1) Decide whether the CAN network is already terminated, or if the SDM-CAN
needs to provide termination. In most instances the network will already be
terminated and so the default setting is no termination.
2) Decide whether to operate the SDM-CAN in a mode where it is isolated from
the CAN network. This is the ‘safest’ mode of operation as it minimises the
risk of corrupting the CAN data by the formation of grounds loops which
could inject noise onto the CAN-Bus. The default setting is to run in isolated
mode.
3) If running in isolated mode decide whether the SDM-CAN will supply power
via a built-in DC-DC converter for the isolated CAN interface components, or
whether power will be sourced from an external supply. Using a converter
adds 40-50mA to the power consumption of the SDM-CAN when it is active.
However, if a converter is not used, power must be provided from elsewhere
(see below). The default setting is for the converter to be OFF, although for
many applications you may need to turn it on once you have considered the
implications for your power supply.
4) Decide whether the transmit functions of the SDM-CAN interface need to be
enabled in hardware. The disabled mode of operation is the safest, especially
in vehicle applications, as it avoids the risk of the SDM-CAN sending bad
data onto the CAN network. However, in some modes of operation,
transmission is obligatory e.g. to let the SDM-CAN request data, acknowledge
data or to transmit data onto the bus. If transmission is to be enabled, the
relevant jumpers need to be changed. Additionally transmission must be
enabled by sending the SDM-CAN an instruction which both enables and
specifies the method of transmission. See Section 3.3, data type 32, below.
Access to the jumpers requires the removal of the lid of the SDM-CAN. Please
follow anti-static precautions during the removal of the lid and also when
changing the jumpers. Refer to Figure 2-1 for details of the jumper positions.
Labels are also provided in white writing on the circuit board.
If white jumper block not fitted then refer to Figure 2-2 for isolation enabled and
Figure 2-3 for isolation disabled.
2-2