AN1077 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'AN1077' PDF : 14 Pages View PDF
OVERVIEW OF ENHANCED CAN CONTROLLERS FOR ST7 AND ST9 MCUS
3.4 MESSAGE FILTERING
Figure 2. Filter Scale and Configuration
Filter Scale Configuration
Filter Scale Config. Bits1
Identifier
Mask/Ident.
Bit Mapping
Identifier
Mask/Ident.
Identifier
Mask/Ident.
Bit Mapping
One 32-Bit Filter
CFxR0
CFxR4
STID10:3
CFxR1
CFxR5
STID2:0 RTR IDE EXID17:15
Two 16-Bit Filters
CFxR0
CFxR2
CFxR1
CFxR3
CFxR4
CFxR6
STID10:3
CFxR5
CFxR7
STID2:0 RTR IDE EXID17:15
FSCx = 3
CFxR2
CFxR6
EXID14:7
FSCx = 2
CFxR3
CFxR7
EXID6:0
Identifier
Mask/Ident.
Identifier
Mask/Ident.
Identifier
Mask/Ident.
One 16-Bit / Two 8-Bit Filters
CFxR0
CFxR2
CFxR1
CFxR3
CFxR4
CFxR5
CFxR6
CFxR7
Identifier
Mask/Ident.
Four 8-Bit Filters
CFxR0
CFxR1
Identifier
CFxR2
Mask/Ident. CFxR3
Identifier
Mask/Ident.
Identifier
Mask/Ident.
Bit Mapping
CFxR4
CFxR5
CFxR6
CFxR7
STID10:3
FSCx = 1
FSCx = 0
x = filter number
1 These bits are located in the CFCR registers
One of the bxCAN’s key improvements is the extended filter mechanism avoiding any mes-
sage filtering by software. This pure hardware filtering makes the CPU performance inde-
pendent from the CAN bus traffic.
Hardware filtering:
s Saves CPU resources required for software filtering
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