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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
346 of 808
NXP Semiconductors
UM10360
Chapter 16: LPC17xx CAN1/2
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 LPC17xx is in Deep Sleep or Power-down mode, CAN activity will wake up the
device if the CAN activity interrupt is enabled. See
.
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
Receive and Transmit interrupt request from each controller is assigned its own channel in
the NVIC, and can have its own interrupt service routine. The “other status” interrupts from
all of the CAN controllers, and the Acceptance Filter LUTerr condition, are ORed into one
NVIC channel.
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.
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.