50.9.6 CAN Baudrate Register

This register can only be written if the WPEN bit is cleared in the CAN Write Protection Mode Register.

Any modification on one of the CAN_BR fields must be done while the CAN module is disabled.

To compute the different bit timings, see CAN Bit Timing Configuration.

Name:	CAN_BR
Offset:	0x0014
Reset:	0x00000000
Property:	Read/Write


Bit	31	30	29	28	27	26	25	24
								SMP
Access								R/W
Reset								0


Bit	23	22	21	20	19	18	17	16
		BRP[6:0]
Access		R/W	R/W	R/W	R/W	R/W	R/W	R/W
Reset		0	0	0	0	0	0	0


Bit	15	14	13	12	11	10	9	8
			SJW[1:0]			PROPAG[2:0]
Access			R/W	R/W		R/W	R/W	R/W
Reset			0	0		0	0	0


Bit	7	6	5	4	3	2	1	0
		PHASE1[2:0]				PHASE2[2:0]
Access		R/W	R/W	R/W		R/W	R/W	R/W
Reset		0	0	0		0	0	0

Bit 24 – SMP Sampling Mode

0 (ONCE): The incoming bit stream is sampled once at sample point.

1 (THREE): The incoming bit stream is sampled three times with a period of a peripheral clock, centered on sample point.

SMP Sampling mode is automatically disabled if BRP = 0.

Bits 22:16 – BRP[6:0] Baudrate Prescaler

This field allows user to program the period of the CAN system clock to determine the individual bit timing.

t_{CSC} = (BRP + 1) / t_{peripheral clock}

The BRP field must be within the range [1, 0x7F], i.e., BRP = 0 is not authorized.

Bits 13:12 – SJW[1:0] Re-synchronization Jump Width

To compensate for phase shifts between clock oscillators of different controllers on bus. The controller must re-synchronize on any relevant signal edge of the current transmission. The synchronization jump width defines the maximum of clock cycles a bit period may be shortened or lengthened by re-synchronization.

t_{SJW} = t_{CSC} \times (SJW + 1)

Bits 10:8 – PROPAG[2:0] Programming Time Segment

This part of the bit time is used to compensate for the physical delay times within the network.

t_{PRS} = t_{CSC} \times (PROPAG + 1)

Bits 6:4 – PHASE1[2:0] Phase 1 Segment

This phase is used to compensate for edge phase error.

t_{PHS1} = t_{CSC} \times (PHASE1 + 1)

Bits 2:0 – PHASE2[2:0] Phase 2 Segment

This phase is used to compensate the edge phase error.

t_{PHS2} = t_{CSC} \times (PHASE2 + 1)

Note: PHASE2 value must be different from 0.