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 354 of 841
NXP Semiconductors
UM10360
Chapter 16: LPC176x/5x CAN1/2
[3] A write access to the bits MOD.1 and MOD.2 is possible only if the Reset Mode is entered previously.
[4] Transmit Priority Mode is explained in more detail in Section 16.5.3 “
Transmit Buffers (TXB)”.
[5] The CAN Controller will enter Sleep Mode, if the Sleep Mode bit is set '1' (sleep), there is no bus activity, and none of the CAN interrupts
is pending. Setting of SM with at least one of the previously mentioned exceptions valid will result in a wake-up interrupt. The CAN
Controller will wake up if SM is set LOW (wake-up) or there is bus activity. On wake-up, a Wake-up Interrupt is generated. A sleeping
CAN Controller which wakes up due to bus activity will not be able to receive this message until it detects 11 consecutive recessive bits
(Bus-Free sequence). Note that setting of SM is not possible in Reset Mode. After clearing of Reset Mode, setting of SM is possible only
when Bus-Free is detected again.
[6] The LOM and STM bits can only be written if the RM bit is 1 prior to the write operation.
16.7.2 CAN Command Register (CAN1CMR - 0x4004 x004, CAN2CMR -
0x4004 8004)
Writing to this write-only register initiates an action within the transfer layer of the CAN
Controller. Reading this register yields zeroes.
At least one internal clock cycle is needed for processing between two commands.
Table 318. CAN Command Register (CAN1CMR - address 0x4004 4004, CAN2CMR - address 0x4004 8004) bit
description
Bit Symbol Value Function Reset
Value
RM
Set
0
[1][2]
TR Transmission Request. 0 0
0 (absent) No transmission request.
1 (present) The message, previously written to the CANxTFI, CANxTID, and
optionally the CANxTDA and CANxTDB registers, is queued for
transmission from the selected Transmit Buffer. If at two or all three of
STB1, STB2 and STB3 bits are selected when TR=1 is written, Transmit
Buffer will be selected based on the chosen priority scheme (for details
see Section 16.5.3 “
Transmit Buffers (TXB)”)
1
[1][3]
AT Abort Transmission. 0 0
0 (no action) Do not abort the transmission.
1 (present) if not already in progress, a pending Transmission Request for the
selected Transmit Buffer is cancelled.
2
[4]
RRB Release Receive Buffer. 0 0
0 (no action) Do not release the receive buffer.
1 (released) The information in the Receive Buffer (consisting of CANxRFS,
CANxRID, and if applicable the CANxRDA and CANxRDB registers) is
released, and becomes eligible for replacement by the next received
frame. If the next received frame is not available, writing this command
clears the RBS bit in the Status Register(s).
3
[5]
CDO Clear Data Overrun. 0 0
0 (no action) Do not clear the data overrun bit.
1 (clear) The Data Overrun bit in Status Register(s) is cleared.
4
[1][6]
SRR Self Reception Request. 0 0
0 (absent) No self reception request.
1 (present) The message, previously written to the CANxTFS, CANxTID, and
optionally the CANxTDA and CANxTDB registers, is queued for
transmission from the selected Transmit Buffer and received
simultaneously. This differs from the TR bit above in that the receiver is
not disabled during the transmission, so that it receives the message if its
Identifier is recognized by the Acceptance Filter.
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