Preface
MPC5565 Microcontroller Reference Manual, Rev. 1.0
21-12
Freescale Semiconductor
21.3.3.2
Control Register (CAN
x
_CR)
CAN
x
_CR is defined for specific FlexCAN2 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 (for example, bus-off, error). It also determines the division factor for the
clock prescaler. BOFFMSK, ERRMSK, and BOFFREC bits can be accessed at any time. CANx_CR is
unaffected by soft reset, which occurs when CAN_MCR[SOFTRST] is asserted.
16-25
Reserved.
26–31
MAXMB[0:5]
Maximum number of message buffers. This 6-bit field defines the maximum number of message buffers of
the FlexCAN2 module. The reset value (0x0F) is equivalent to 16 MB configuration. This field should be
changed only while the module is in freeze mode.
Note:
MAXMB has to be programmed with a value smaller or equal to the number of available message
buffers, otherwise FlexCAN2 will not transmit or receive frames.
Address: Base + 0x0004
Access: User read/write
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
R
PRESDIV
RJW
PSEG1
PSEG2
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
R BOFF
MSK
ERR
MSK
CLK_
SRC
LPB
TWRN
MSK
RWRN
MSK
0
0
SMP
BOFF
REC
TSYN LBUF LOM
PROPSEG
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
CAN
x
_CR is unaffected by soft reset (which occurs when CAN_MCR[SOFTRST] is asserted).
Figure 21-4. Control Register (CAN
x
_CR)
Table 21-8. CAN
x
_CR Field Descriptions
Bits
Description
0–7
PRESDIV[0:7]
Prescaler division factor. Defines the ratio between the CPI clock frequency and the serial clock (SCK)
frequency. The SCK period defines the time quantum of the CAN protocol. For the reset value, the SCK
frequency is equal to the CPI clock frequency. The maximum value of this register is 0xFF, that gives a
minimum SCK frequency equal to the CPI clock frequency divided by 256. For more information, refer to
Section 21.4.5.4, “Protocol Timing
.”
8–9
RJW[0:1]
Resync jump width. Defines the maximum number of time quanta
1
that a bit time can be changed by one
re-synchronization. The valid programmable values are 0
–
3.
Table 21-7. CAN
x
_MCR Field Descriptions (continued)
Field
Description
Maximum MBs in use
MAXMB
1
+
=
S-clock frequency
CPI clock frequency
PRESDIV
1
+
-----------------------------------------------------
=
Resync Jump Width
RJW + 1
=
Содержание MPC5565
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