
FlexCAN
23-28
Freescale Semiconductor
23.4
Initialization/Application Information
Initialization of the FlexCAN includes the initial configuration of the message buffers and configuration
of the CAN communication parameters following a reset, as well as any reconfiguration that may be
required during operation. The FlexCAN module may be reset in three ways:
•
Device level hard reset—resets all memory mapped registers asynchronously
•
Device level soft reset—resets some of the memory mapped registers synchronously (refer to
to see which registers are affected by soft reset)
•
CANMCR[SOFT_RST] bit—has the same effect as the device level soft reset
Soft reset is synchronous and has to follow an internal request/acknowledge procedure across clock
domains. Therefore, it may take some time to fully propagate its effects. The CANMCR[SOFT_RST] bit
remains asserted while soft reset is pending, so software can poll this bit to know when the reset has
completed. Also, soft reset can not be applied while clocks are shut down in any of the low power modes.
The low power mode should be exited and the clocks resumed before applying soft reset.
The clock source, CANCTRL[CLK_SRC], should be selected while the module is in disable mode. After
the clock source is selected and the module is enabled (CANMCR[MDIS] bit cleared), the FlexCAN
automatically enters freeze mode. In freeze mode, the FlexCAN is un-synchronized to the CAN bus, the
CANMCR register’s HALT and FRZ bits are set, the internal state machines are disabled, and the
CANMCR register’s FRZ_ACK and NOT_RDY bits are set. The CANTX pin is in recessive state and the
FlexCAN does not initiate any transmission or reception of CAN frames. The message buffers are not
affected by reset, so they are not automatically initialized.
For any configuration change/initialization, the FlexCAN must be in freeze mode (see
). The following is a generic initialization sequence applicable to the FlexCAN module:
1. Initialize all operation modes in the CANCTRL register.
a) Initialize the bit timing parameters PROPSEG, PSEGS1, PSEG2, and RJW.
b) Select the S-clock rate by programming the PRESDIV field.
c) Select the internal arbitration mode via the LBUF bit.
2. Initialize message buffers.
a) The control/status word of all message buffers must be written as an active or inactive message
buffer.
b) All other entries in each message buffer should be initialized as required.
3. Initialize RXGMASK, RX14MASK, and RX15MASK registers for acceptance mask as needed.
8 .. 15
7
1 .. 4
9 .. 16
8
1 .. 4
Table 23-15. CAN Standard Compliant Bit Time Segment Settings (continued)
Time Segment 1
Time Segment 2
Re-synchronization
Jump Width
MCF5329 Reference Manual, Rev 3
Содержание MCF5329
Страница 106: ...ColdFire Core 3 32 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 126: ...Enhanced Multiply Accumulate Unit EMAC 4 20 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 148: ...Cache 5 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 154: ...Static RAM SRAM 6 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 184: ...Power Management 8 18 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 204: ...Reset Controller Module 10 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 220: ...System Control Module SCM 11 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 228: ...Crossbar Switch XBS 12 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 268: ...General Purpose I O Module 13 40 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 392: ...SDRAM Controller SDRAMC 18 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 436: ...Fast Ethernet Controller FEC 19 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 564: ...Liquid Crystal Display Controller LCDC 22 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 594: ...FlexCAN 23 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 678: ...Pulse Width Modulation PWM Module 26 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 684: ...Watchdog Timer Module 27 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 692: ...Programmable Interrupt Timers PIT0 PIT3 28 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 704: ...DMA Timers DTIM0 DTIM3 29 12 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 720: ...Queued Serial Peripheral Interface QSPI 30 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 754: ...UART Modules 31 34 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 770: ...I2 C Interface 32 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 790: ...Message Digest Hardware Accelerator MDHA 33 20 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 866: ...Debug Module 36 50 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Страница 902: ...Register Memory Map Quick Reference A 26 Freescale Semiconductor MCF5329 Reference Manual Rev 3...