STMicroelectronics SPC572L series Reference Manual page 1425

RM0400
filter the corresponding FACT bit in IFER needs to be set. There are two modes possible for
each identifier depending on the corresponding IFM bit of IFMR.
Identifier list mode
th
If the n
this mode, the maximum number of filters that can be configured for transmission/reception
equals no_of_filters, depending on the FACT bit of IFER. In this mode the identifier received
should match bit by bit to the ID field of IFCR2n or IFCR2n+1 (if the corresponding FACT bit
is set).
Identifier mask mode
If the number of filters required is more than no_of_filters, then filters should be configured
in Mask mode. If the n
a mask for it. The FACT bit for filter 2n+1 has no effect in this case. In this mode, if the x
of the mask is set, then the x
If there is a match of identifier with the mth filter in any mode, then m+1 is loaded in the IFMI
register by hardware. No match condition is denoted by IFMI = 0.
Upon matching DFL (2:0), the CCS and DIR bits of the BIDR register are copied from the
filter by hardware and from then on, the BIDR register is read-only until the end of the frame.
Now if the DIR bit of BIDR is set, then a TXI interrupt is generated if the HRIE bit of LINIER
is set. In this case, software uses the IFMI register to transfer the relevant data from the
RAM area to BDR, and after a complete transfer the DTRQ bit of LINCR2 is set to start the
transmission. If the DIR bit is cleared then an RXI interrupt is generated (provided DRIE bit
of LINIER is set) when the checksum has been received and there is no checksum error.
In case of no filter match condition (IFMI = 0) and if the BF bit of LINCR1 is set, then an RXI
is generated. Now it is the responsibility of software to configure BIDR and start
transmission (by loading the BDR buffer and setting the DTRQ bit of LINCR2) or discard
reception (by setting the DDRQ bit of LINCR2). If the BF bit is reset, then the receiver
discards the received identifier and turns to Idle state in search of a new break.
Note: If one identifier matches with two filters (one is in the list and the other in Mask mode) then
List mode prevails over Mask mode. In Mask mode, if two filters match with the identifier
then the filter having the lower number prevails.
bit of IFMR is cleared, then filter number 2n and 2n+1 is in identifier list mode. In
th
bit of IFMR is set, then filter number 2n is the filter and 2n+1 acts as
th
DocID027809 Rev 4
bit of the received identifier must match the x
LINFlexD
th
bit
th
bit of filter.
1425/2058
1506