NXP Semiconductors MPC5605BK, Reference Manual

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Chapter 24 LIN Controller (LINFlexD)
MPC5606BK Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 479
To fulfill this requirement, the LINFlexD controller provides configurable filters in order to request
software intervention only if needed. This hardware filtering saves CPU resources, which would otherwise
be needed by software for filtering.
The filtering is accomplished through the use of IFCR registers. These registers have the names IFCR0
through IFCR. This section also uses the nomenclature IFCR
2n
and IFCR
2n+1
; in this nomenclature, n is
an integer, and the corresponding IFCR register is calculated using the formula in the subscript.
24.7.3.1 Filter submodes
Usually each of the 16 IFCRs is used to filter one dedicated identifier, but this means that the LINFlexD
controller could filter a maximum of 16 identifiers. In order to be able to handle more identifiers, the filters
can be configured to operate as masks.
Table 24-3 describes the two available filter submodes.
The bit mapping and register organization in these two submodes is shown in Figure 24-9 .
Figure 24-9. Filter configuration—register organization
Table 24-3. Filter submodes
Submode Description
Identifier list Both filter registers are used as identifier registers. All bits of the incoming identifier must match
the bits specified in the filter register. This is the default submode for the LINFlexD controller.
Mask The identifier registers are associated with mask registers specifying which bits of the identifier
are handled as “must match” or as “don’t care”.
IFCR
x
Identifier
ID
Bit Mapping
Identifier filter register organization
CCS DIR
Identifier filter configuration
IFCR
2n
Identifier
Identifier
IFCR
2n+1
IFM = 0
Identifier filter submode
IFCR
2n
Identifier
Mask
IFCR
2n+1
IFM = 1
Identifier list submode
Mask submode
DFL