ST ST10F276E - Page 438

CAN modules UM0404
438/564 DocID13284 Rev 2
CAN1IF2DA2 (EF50h) XBUS Reset Value: 0000h
CAN2IF2DA2 (EE50h) XBUS Reset Value: 0000h
CAN1IF2DB1 (EF52h) XBUS Reset Value: 0000h
CAN2IF2DB1 (EE52h) XBUS Reset Value: 0000h
CAN1IF2DB2 (EF54h) XBUS Reset Value: 0000h
CAN2IF2DB2 (EE54h) XBUS Reset Value: 0000h
In a CAN Data Frame, Data(0) is the first, Data(7) is the last byte to be transmitted or
received. In CAN’s serial bit stream, the MSB of each byte will be transmitted first.
When the Message Handler stores a Data Frame, it will write all the eight data bytes into a
Message Object. If the Data Length Code is less than 8, the remaining bytes of the
Message Object will be overwritten by non specified values.
Message object in the message memory
There are 32 Message Objects in the Message RAM. To avoid conflicts between CPU
access to the Message RAM and CAN message reception and transmission, the CPU
cannot directly access the Message Objects, these accesses are handled via the IFx
Interface Registers.
Next diagram gives an overview of the two structures of a Message Object in the Message
Memory.
1514131211109876543210
Data(3) Data(2)
RW RW
1514131211109876543210
Data(5) Data(4)
RW RW
1514131211109876543210
Data(7) Data(6)
RW RW
Message object
UMask Msk(28:0) MXtd MDir EoB NewDat MsgLst RxIE TxIE IntPnd RmtEn TxRqst
MsgVal ID(28:0) Xtd Dir DLC(3:0) Data 0 Data 1 Data 2 Data 3 Data 4 Data 5 Data 6 Data 7