Controller Area Network (FlexCAN)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
Freescale Semiconductor
25-13
Preliminary
SOFTRST
Soft Reset. When asserted, FlexCAN resets its internal state machines and some of the memory-mapped
registers. The following registers are affected by soft reset:
• CANx_MCR (except the MDIS bit)
• CANx_TIMER
• CANx_ECR
• CANx_ESR
• CANx_IMASK1
• CANx_IMASK2
• CANx_IFLAG1
• CANx_IFLAG2
Configuration registers that control the interface to the CAN bus are not affected by soft reset. The following
registers are unaffected:
• CANx_CTRL
• CANx_RXGMASK
• CANx_RX14MASK
• CANx_RX15MASK
• all message buffers
The SOFTRST bit can be asserted directly by the CPU when it writes to the CANx_MCR, but it is also
asserted when global soft reset is requested at MCU level. Because soft reset is synchronous and has to
follow a request/acknowledge procedure across clock domains, it may take some time to fully propagate its
effect. The SOFTRST bit remains asserted while reset is pending, and is automatically negated when reset
completes. Therefore, software can poll this bit to know when the soft reset has completed.
0 No reset request.
1 Resets values in registers indicated above.
FRZACK
Freeze Mode Acknowledge. Indicates that FlexCAN is in freeze mode and its prescaler is stopped. The freeze
mode request cannot be granted until current transmission and reception processes have finished. Therefore
the software can poll the FRZACK bit to know when FlexCAN has actually entered freeze mode. If freeze
mode request is negated, then this bit is negated once the FlexCAN prescaler is running again. If freeze
mode is requested while FlexCAN is disabled, then the FRZACK bit will only be set when the low-power mode
is exited. See
Section 25.4.8.1, “Freeze Mode
,” for more information.
0 FlexCAN not in freeze mode, prescaler running.
1 FlexCAN in freeze mode, prescaler stopped.
bits 8–9
Reserved.
WRNEN
Warning Interrupt Enable. When asserted, this bit enables the generation of the TWRNINT and RWRNINT
flags in the error and status register. If WRNEN is negated, the TWRNINT and RWRNINT flags will always
be 0, independent of the values of the error counters, and no warning interrupt will ever be generated.
1 = TWRNINT and RWRNINT bits are set when the respective error counter transition from <96
to
≥
96.
0 = TWRNINT and RWRNINT bits are zero, independent of the values in the error counters.
LPM_SACK Low-Power Mode Acknowledge. Indicates whether FlexCAN is disabled. This cannot be performed until all
current transmission and reception processes have finished, so the CPU can poll the MDISACK bit to know
when FlexCAN has actually been disabled. See
Section 25.4.8.2, “Module Disabled Mode
,” for more
information.
0 FlexCAN not disabled.
1 FlexCAN is disabled.
bits 12–13
Reserved.
Table 25-7. CANx_MCR Field Descriptions (continued)
Field
Description