UMAX141100 Version 1.0.6.
Preliminary Documentation – May be subject to change
13 - 36
2.4.
CAN
Receive
Filtering
Figure 5 – CAN Receive Filtering
By default the device won’t read in all received CAN messages. With the CAN receive filtering
functions, the user can change this behaviour.
Disable CAN fitering
removes all CAN receive
filtering and makes the CAN2BT device capable of receiving all CAN frames on the bus. With CAN
filtering disabled, the CAN2BT device is invisible to the CAN bus. This is the mode that is preferred
for using the device as a bridge between two CAN buses.
Enable CAN filtering
restores the default CAN receive filtering and makes the CAN2BT device
visible to the CAN bus (it will respond to Address Claim messages).
Add CAN RX filter
lets the user to define a single CAN filter and optional mask that are added to
the low level (HW) CAN receive filter registers. Please note, that if the mask is not specified, the
firmware uses a default mask of 29 (or 11) bits wide that will compare all bits in the received CAN
frame against the specified filter.
Up to 28 filter definitions will be accepted. The
Remove CAN RX filter
will remove the specified filter
(the removal is done by comparing the IDs of the configured filters and the ID specified to be
removed).
The CAN filter definition for adding and removing filters is as follows:
bit 31
bit 30
bits 29-0
Use ExtID
Use RTR
Filter ID
Table 1 – CAN Rx filter definition
Example
29bit
ID
filter
&
mask
for
receiving
all
(J1939)
frames
with
Source
Address
0xF9
Filter:
800000F9
, Mask:
FF
Example
11bit
ID
filter
&
mask
for
receiving
ID
0x701
(CANopen
master
HB)
Filter:
701
, Mask:
7FF
