MC68336/376
CAN 2.0B CONTROLLER MODULE (TouCAN)
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
13-8
Table 13-7 shows mask examples for normal and extended messages. Refer to
13.4.3 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
configure the bit timing parameters. The prescaler divide register (PRESDIV) allows
the user to select the ratio used to derive the S-clock from the system clock. The time
quanta clock operates at the S-clock frequency. Table 13-8 provides examples of sys-
Table 13-6 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 13-7 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.