SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The DCAN message RAM contains message objects and parity bits for the message objects. There are up to 64 message objects in the message RAM.
During normal operation, accesses to the message RAM are performed via the interface register sets, and the software cannot directly access the message RAM.
The interface register sets IF1 and IF2 provide indirect read/write access from the software to the message RAM. The IF1 and IF2 register sets can buffer control and user data to be transferred to and from the message objects.
The third interface register set IF3 can be configured to automatically receive control and user data from the message RAM when a message object has been updated after reception of a CAN message. The software does not need to initiate the transfer from message RAM to IF3 register set.
The message handler avoids potential conflicts between concurrent accesses to message RAM and CAN frame reception/transmission.
There are two modes where the message RAM can be directly accessed by the software:
Writes to the DCAN RAM must not be done while it is in low-power mode. If such writes occur, the behavior is undefined and RAM content is corrupted. It has to be ensured in software that the low-power mode is removed from the DCAN RAM before writing to it.