Can Controller Initialization; Initialization Of Can Module; Initialization Of Message Buffer; Redefinition Of Message Buffer - NEC V850ES/F 3-L Series User Manual

Chapter 18

18.8 CAN Controller Initialization

18.8.1 Initialization of CAN module

18.8.2 Initialization of message buffer

18.8.3 Redefinition of message buffer

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Before CAN module operation is enabled, the CAN module system clock
needs to be determined by setting the CCP[3:0] bits of the CnGMCS register
by software. Do not change the setting of the CAN module system clock after
CAN module operation is enabled.
The CAN module is enabled by setting the GOM bit of the CnGMCTRL
register.
For the procedure of initializing the CAN module, refer to "Operation of CAN
Controller" on page 637.
After the CAN module is enabled, the message buffers contain undefined
values. A minimum initialization for all the message buffers, even for those not
used in the application, is necessary before switching the CAN module from
the initialization mode to one of the operation modes.
• Clear the RDY, TRQ, and DN bits of all CnMCTRLm registers to 0.
• Clear the MA0 bit of all CnMCONFm registers to 0.
Redefining a message buffer means changing the ID and control information of
the message buffer while a message is being received or transmitted, without
affecting other transmission/reception operations.
To redefine message buffer in initialization mode
Place the CAN module in the initialization mode once and then change the ID
and control information of the message buffer in the initialization mode. After
changing the ID and control information, set the CAN module to an operation
mode.
To redefine message buffer during reception
Perform redefinition as shown in Figure 18-38.
To redefine message buffer during transmission
To rewrite the contents of a transmit message buffer to which a transmission
request has been set, perform transmission abort processing (see
"Transmission abort process except for in normal operation mode with
automatic block transmission (ABT)" on page 616 and "Transmission abort
process except for ABT transmission in normal operation mode with automatic
block transmission (ABT)" on page 616). Confirm that transmission has been
aborted or completed, and then redefine the message buffer. After redefining
User's Manual U18743EE1V2UM00
CAN Controller (CAN)