STMicroelectronics SPC572L series Reference Manual page 1064

CAN Subsystem
Related configuration registers are:
•
Global Filter Configuration (GFC)
•
Standard ID Filter Configuration (SIDFC)
•
Extended ID Filter Configuration (XIDFC)
•
Extended ID AND Mask (XIDAM)
Depending on the configuration of the filter element (SFEC/EFEC) a match triggers one of
the following actions:
•
Store received frame in FIFO 0 or FIFO 1
•
Store received frame in Rx Buffer
• Reject received frame
•
Set High Priority Message interrupt flag IR[HPM]
• Set High Priority Message interrupt flag IR[HPM] and store received frame in FIFO 0 or
FIFO 1
Note: When an accepted message is written to one of the two Rx FIFOs, or into a Rx Buffer, the
unmodified received identifier is stored independent of the filter(s) used. The result of the
acceptance filter process is strongly depending on the sequence of configured filter
elements.
44.3.10.1.1 Range filter
The filter matches for all received frames with Message IDs in the range defined by
SF1ID/SF2ID resp. EF1ID/EF2ID. There are two possibilities when range filtering is used
together with extended frames:
•
EFT = "00": The Message ID of received frames is ANDed with the Extended ID AND
Mask (XIDAM) before the range filter is applied
•
EFT = "11": The Extended ID AND Mask (XIDAM) is not used for range filtering
44.3.10.1.2 Filter for specific IDs
A filter element can be configured to filter for one or two specific Message IDs. To filter for
one specific Message ID, the filter element has to be configured with SF1ID = SF2ID resp.
EF1ID =EF2ID.
44.3.10.1.3 Filter for dedicated IDs
A filter element can be configured to filter for one or two specific Message IDs. To filter for
one specific Message ID, the filter element has to be configured with SF1ID = SF2ID resp.
EF1ID = EF2ID.
44.3.10.1.4 Classic Bit Mask Filter
Classic bit mask filtering is intended to filter groups of Message IDs by masking single bits of
a received Message ID. With classic bit mask filtering SF1ID/EF1ID is used as Message ID
filter, while SF2ID/EF2ID is used as filter mask.
A zero bit at the filter mask will mask out the corresponding bit position of the configured ID
filter, e.g. the value of the received Message ID at that bit position is not relevant for
acceptance filtering. Only those bits of the received Message ID where the corresponding
mask bits are one are relevant for acceptance filtering. In case all mask bits are one, a
1064/2058 DocID027809 Rev 4
RM0400