MC9S12GRMV1 Datasheet, PDF (593/1292 Pages) Freescale Semiconductor, Inc – MC9S12G Family Reference Manual and Data Sheet

Freescale’s Scalable Controller Area Network (S12MSCANV3)
Table 18-7. Baud Rate Prescaler
BRP5
0
0
0
0
:
1
BRP4
0
0
0
0
:
1
BRP3
0
0
0
0
:
1
BRP2
0
0
0
0
:
1
BRP1
0
0
1
1
:
1
BRP0
0
1
0
1
:
1
Prescaler value (P)
1
2
3
4
:
64
18.3.2.4 MSCAN Bus Timing Register 1 (CANBTR1)
The CANBTR1 register configures various CAN bus timing parameters of the MSCAN module.
Module Base + 0x0003
Access: User read/write¹
7
R
SAMP
W
6
TSEG22
5
TSEG21
4
TSEG20
3
TSEG13
2
TSEG12
Reset:
0
0
0
0
0
0
Figure 18-7. MSCAN Bus Timing Register 1 (CANBTR1)
1 _{Read: Anytime}
Write: Anytime in initialization mode (INITRQ = 1 and INITAK = 1)
1
TSEG11
0
0
TSEG10
0
Table 18-8. CANBTR1 Register Field Descriptions
Field
Description
7
SAMP
Sampling — This bit determines the number of CAN bus samples taken per bit time.
0 One sample per bit.
1 Three samples per bit¹.
If SAMP = 0, the resulting bit value is equal to the value of the single bit positioned at the sample point. If
SAMP = 1, the resulting bit value is determined by using majority rule on the three total samples. For higher bit
rates, it is recommended that only one sample is taken per bit time (SAMP = 0).
6-4
Time Segment 2 — Time segments within the bit time fix the number of clock cycles per bit time and the location
TSEG2[2:0] of the sample point (see Figure 18-44). Time segment 2 (TSEG2) values are programmable as shown in
Table 18-9.
3-0
Time Segment 1 — Time segments within the bit time fix the number of clock cycles per bit time and the location
TSEG1[3:0] of the sample point (see Figure 18-44). Time segment 1 (TSEG1) values are programmable as shown in
Table 18-10.
1 _{In this case, PHASE_SEG1 must be at least 2 time quanta (Tq).}
MC9S12G Family Reference Manual, Rev.1.23
Freescale Semiconductor
595