Information
42.3.3 Control 1 Register (CANx_CTRL1)
This register is defined for specific FlexCAN control features related to the CAN bus,
such as bit-rate, programmable sampling point within an Rx bit, Loop Back Mode,
Listen-Only Mode, Bus Off recovery behavior and interrupt enabling (Bus-Off, Error,
Warning). It also determines the Division Factor for the clock prescaler.
Addresses: CAN0_CTRL1 is 4002_4000h base + 4h offset = 4002_4004h
CAN1_CTRL1 is 400A_4000h base + 4h offset = 400A_4004h
Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
R
PRESDIV RJW PSEG1 PSEG2
W
Reset
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Bit
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R
BOFFMSK
ERRMSK
CLKSRC
LPB
TWRNMSK
RWRNMSK
0
SMP
BOFFREC
TSYN
LBUF
LOM
PROPSEG
W
Reset
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CANx_CTRL1 field descriptions
Field Description
31–24
PRESDIV
Prescaler Division Factor
This 8-bit field defines the ratio between the PE clock frequency and the Serial Clock (Sclock) frequency.
The Sclock period defines the time quantum of the CAN protocol. For the reset value, the Sclock
frequency is equal to the PE clock frequency. The Maximum value of this field is 0xFF, that gives a
minimum Sclock frequency equal to the PE clock frequency divided by 256. See Section "Protocol
Timing". This field can only be written in Freeze mode as it is blocked by hardware in other modes.
Sclock frequency = PE clock frequency / (PRESDIV + 1)
23–22
RJW
Resync Jump Width
This 2-bit field defines the maximum number of time quanta that a bit time can be changed by one re-
synchronization. (One time quantum is equal to the Sclock period.) The valid programmable values are 0–
3. This field can only be written in Freeze mode as it is blocked by hardware in other modes.
Resync Jump Width = RJW + 1.
21–19
PSEG1
Phase Segment 1
This 3-bit field defines the length of Phase Buffer Segment 1 in the bit time. The valid programmable
values are 0–7. This field can only be written in Freeze mode as it is blocked by hardware in other modes.
Phase Buffer Segment 1 = (PSEG1 + 1) x Time-Quanta.
18–16
PSEG2
Phase Segment 2
Table continues on the next page...
Chapter 42 CAN (FlexCAN)
K10 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc. 1093