Datasheet

UM10398 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
User manual Rev. 12.3 — 10 June 2014 313 of 547
NXP Semiconductors
UM10398
Chapter 16: LPC111x/LPC11Cxx C_CAN controller
The Arbitration Registers (ID28:0 and XTD bit) are given by the application. They define
the identifier and the type of the outgoing message. If an 11-bit Identifier (“Standard
Frame”) is used, it is programmed to ID28. In this case ID18, ID17 to ID0 can be
disregarded.
If the TXIE bit is set, the INTPND bit will be set after a successful transmission of the
Message Object.
If the RMTEN bit is set, a matching received Remote Frame will cause the TXRQST bit to
be set, and the Remote Frame will autonomously be answered by a Data Frame.
The Data Registers (DLC3:0, Data0:7) are given by the application. TXRQST and RMTEN
may not be set before the data is valid.
The Mask Registers (Msk28-0, UMASK, MXTD, and MDIR bits) may be used
(UMASK=’1’) to allow groups of Remote Frames with similar identifiers to set the TXRQST
bit. For details see Section 16.7.3.4.2
. The DIR bit should not be masked.
16.7.3.7 Updating a transmit object
The CPU may update the data bytes of a Transmit Object any time via the IFx Interface
registers. Neither MSGVAL nor TXRQST have to be reset before the update.
Even if only a part of the data bytes are to be updated, all four bytes of the corresponding
IFx Data A Register or IFx Data B Register have to be valid before the content of that
register is transferred to the Message Object. Either the CPU has to write all four bytes
into the IFx Data Register or the Message Object is transferred to the IFx Data Register
before the CPU writes the new data bytes.
When only the (eight) data bytes are updated, first 0x0087 is written to the Command
Mask Register. Then the number of the Message Object is written to the Command
Request Register, concurrently updating the data bytes and setting TXRQST.
To prevent the reset of TXRQST at the end of a transmission that may already be in
progress while the data is updated, NEWDAT has to be set together with TXRQST. For
details see Section 16.7.3.3
.
When NEWDAT is set together with TXRQST, NEWDAT will be reset as soon as the new
transmission has started.
16.7.3.8 Configuration of a receive object
Table 277 shows how a receive object should be initialized by software (see also
Table 254
)
Table 276. Initialization of a transmit object
MSGVAL Arbitration
bits
Data bits Mask bits EOB DIR NEWDAT
1 application
dependent
application
dependent
application
dependent
110
MSGLST RXIE TXIE INTPND RMTEN TXRQST
0 0 application
dependent
0 application
dependent
0