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OVERVIEW OF ENHANCED CAN CONTROLLERS FOR ST7 AND ST9 MCUS

3.4 MESSAGE FILTERING

Figure 2. Filter Scale and Configuration

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

One 32-Bit Filter

Two 16-Bit Filters

One 16-Bit / Two 8-Bit Filters

Four 8-Bit Filters

CFxR0

CFxR4

CFxR1

CFxR5

CFxR2

CFxR6

CFxR3

CFxR7

CFxR0

CFxR2

CFxR1

CFxR3

CFxR4

CFxR6

CFxR5

CFxR7

CFxR0

CFxR2

CFxR1

CFxR3

CFxR4

CFxR5

CFxR6

CFxR7

CFxR0

CFxR1

CFxR2

CFxR3

CFxR4

CFxR5

CFxR6

CFxR7

x = filter number

FSCx = 3

FSCx = 2

FSCx = 1

FSCx = 0

Filter Scale Configuration

Identifier

Mask/Ident.

Identifier

Mask/Ident.

Identifier

Mask/Ident.

Identifier

Mask/Ident.

Identifier

Mask/Ident.

Identifier

Mask/Ident.

Identifier

Mask/Ident.

Identifier

Mask/Ident.

Identifier

Mask/Ident.

STID10:3

STID2:0 RTR IDE EXID17:15

EXID14:7

EXID6:0

Bit Mapping

STID10:3

Bit Mapping

STID10:3

STID2:0 RTR IDE EXID17:15

Identifier

Mask/Ident.

Bit Mapping