Can Controller Initialization; Initialization Of Can Module; Initialization Of Message Buffer; Redefinition Of Message Buffer - NEC V850E/RS1 User Manual

16.8 CAN Controller Initialization

16.8.1 Initialization of CAN module

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 16.16 "Operation of CAN Controller" on
page 660.

16.8.2 Initialization of message buffer

After the CAN module is enabled, the message buffers contain undefined values. A minimum initializa-
tion for all the message buffers, even for those not used in the application, is necessary before switch-
ing the CAN module from the initialization mode to one of the operation modes.
• Clear the RDY, TRQ, and DN bits of the CnMCTRLm register to 0.
• Clear the MA0 bit of the CnMCONFm register to 0.
Remark:

16.8.3 Redefinition of message buffer

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 opera-
tions.
(1) To redefine message buffer in initialization mode
Place the CAN module in the initialization mode once and then change the ID and control informa-
tion of the message buffer in the initialization mode. After changing the ID and control information,
set the CAN module to an operation mode.
(2) To redefine message buffer during reception
Perform redefinition as shown in Figure 16-60, "Message Buffer Redefinition," on page 663
and Figure 16-61, "Transmitting Message Buffer Redefinition," on page 664.
(3) 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 (refer to 16.10.4 (1)"Transmission abort in normal
operation mode" on page 641 and 16.10.4 (2)"Transmission abort in normal operation
mode with automatic block transmission (ABT)" on page 641). Confirm that transmission has
been aborted or completed, and then redefine the message buffer. After redefining the transmit
message buffer, set a transmission request using the procedure described below. When setting a
transmission request to a message buffer that has been redefined without aborting the transmis-
sion in progress, however, the 1-bit wait time is not necessary.
626
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Chapter 16 FCAN Controller
n = 0, 1
m = 0 to 31
User's Manual U16702EE3V2UD00