UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 372 of 841
NXP Semiconductors
UM10360
Chapter 16: LPC176x/5x CAN1/2
The CAN Controller wakes up (and sets WUI in the CAN Interrupt register if WUIE in the
CAN Interrupt Enable register is 1) in response to a) a dominant bit on the CAN bus, or b)
software clearing SM in the CAN Mode register. A sleeping CAN Controller that wakes up
in response to bus activity is not able to receive an initial message until after it detects
Bus_Free (11 consecutive recessive bits). If an interrupt is pending or the CAN bus is
active when software sets SM, the wake-up is immediate.
Upon wake-up, software needs to do the following things:
1. Write a 1 to the relevant bit(s) in the CANSLEEPCLR register.
2. Write a 0 to the SM bit in the CAN1MOD and/or CAN2MOD register.
3. Write a 1 to the relevant bit(s) in the CANWAKEFLAGS register. Failure to perform
this step will prevent subsequent entry into Power-down mode.
If the LPC176x/5x is in Deep Sleep or Power-down mode, CAN activity will wake up the
device if the CAN activity interrupt is enabled. See Section 4.8 “
Power control”.
16.8.3 Interrupts
Each CAN Controller produces 3 interrupt requests, Receive, Transmit, and “other status”.
The Transmit interrupt is the OR of the Transmit interrupts from the three Tx Buffers. Each
interrupt request will trigger the CAN common interrupt in the NVIC.The “other status”
interrupts from all of the CAN controllers, and the Acceptance Filter LUTerr condition, are
ORed into one NVIC channel.
16.8.4 Transmit priority
If the TPM bit in the CANxMOD register is 0, multiple enabled Tx Buffers contend for the
right to send their messages based on the value of their CAN Identifier (TID). If TPM is 1,
they contend based on the PRIO fields in bits 7:0 of their CANxTFS registers. In both
cases the smallest binary value has priority. If two (or three) transmit-enabled buffers have
the same smallest value, the lowest-numbered buffer sends first.
The CAN controller selects among multiple enabled Tx Buffers dynamically, just before it
sends each message.
16.9 Centralized CAN registers
For easy and fast access, all CAN Controller Status bits from each CAN Controller Status
register are bundled together. Each defined byte of the following registers contains one
particular status bit from each of the CAN controllers, in its LS bits.
All Status registers are read-only and allow byte, half word and word access.
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