
MC68F375
CAN 2.0B CONTROLLER MODULE
MOTOROLA
REFERENCE MANUAL
Rev. 25 June 03
7-8
matched to a locked message buffer, that message will be transferred into that mes-
sage buffer once it is unlocked, regardless of whether that message’s masked
identifier still matches the receive buffer identifier. Table 7-6 shows mask bit values.
Table 7-7 shows mask examples for normal and extended messages. Refer to 7.8 7.4.3 Bit Timing
The TouCAN module uses three 8-bit registers to set up the bit timing parameters
required by the CAN protocol. Control registers 1 and 2 (CANCTRL1, CANCTRL2)
contain the PROPSEG, PSEG1, PSEG2, and the RJW fields which allow the user to
Table 7-6 Receive Mask Register Bit Values
Mask Bit
Values
0
The corresponding incoming ID bit is “don’t care”.
1
The corresponding ID bit is checked against the incoming ID
bit to see if a match exists.
Table 7-7 Mask Examples for Normal/Extended Messages
Message Buffer (MB)
/Mask
Base ID
ID[28:18]
IDE
Extended ID
ID[17:0]
Match
MB2
1 1 1 1 1 1 1 1 0 0 0
0
—
MB3
1 1 1 1 1 1 1 1 0 0 0
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
—
MB4
0 0 0 0 0 0 1 1 1 1 1
0
—
MB5
0 0 0 0 0 0 1 1 1 0 1
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
—
MB14
1 1 1 1 1 1 1 1 0 0 0
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
—
RX Global Mask
1 1 1 1 1 1 1 1 1 1 0
1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 1
—
RX Message In
1 1 1 1 1 1 1 1 0 0 1
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
31
NOTES:
1. Match for extended format (MB3).
1 1 1 1 1 1 1 1 0 0 1
0—
22
2. Match for standard format (MB2).
1 1 1 1 1 1 1 1 0 0 1
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 0
—3
3. No match for MB3 because of ID0.
0 1 1 1 1 1 1 1 0 0 0
0—
—4
4. No match for MB2 because of ID28.
0 1 1 1 1 1 1 1 0 0 0
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
—5
5. No match for MB3 because of ID28, match for MB14.
RX 14 Mask
0 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0
—
RX Message In
1 0 1 1 1 1 1 1 0 0 0
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
—6
6. No match for MB14 because of ID27.
0 1 1 1 1 1 1 1 0 0 0
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
147
7. Match for MB14.
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