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Chapter 34 CAN Controller
2.Register Description
(Note) When 11-bit (“standard”) Identifiers are used for a Message Object, the identifiers of received Data
Frames are written into bits ID28 to ID18. For acceptance filtering, only these bits together with mask
bits Msk28 to Msk18 are considered.
The Arbitration Registers ID28-0, Xtd, and Dir are used to define the identifier and type of outgoing messages
and are used (together with the mask registers Msk28-0, MXtd, and MDir) for acceptance filtering of incoming
messages. A received message is stored into the valid Message Object with matching identifier and Direction=
receive (Data Frame) or Direction= transmit(Remote Frame). Extended frames can be stored only in Message
Objects with Xtd = 1, standard frames in Message Objects with Xtd = 0. If a received message (Data Frame
or Remote Frame) matches with more than one valid Message Object, it is stored into that with the lowest
message number. For details see 4.5 “Acceptance Filtering of Received Messages” on page 726.
(Note) This bit is used to concatenate two ore more Message Objects (up to 32) to build a FIFO Buffer. For
single Message Objects (not belonging to a FIFO Buffer) this bit must always be set to 1. For
details on the concatenation of Message Objects see chapter 4.13 “Configuration of a FIFO Buffer”
on page 728.
1 The 29-bit (“extended”) Identifier will be used for this Message Object.
MXtd Mask Extended Identifier
0 The extended identifier bit (IDE) has no effect on the acceptance filtering
1 The extended identifier bit (IDE) is used for acceptance filtering.
Dir Message Direction
0
Direction = receive: On TxRqst, a Remote Frame with the identifier of this Message Object is
transmitted. On reception of a Data Frame with matching identifier, that message is stored in
this Message Object.
1
Direction = transmit: On TxRqst, the respective Message Object is transmitted as a Data
Frame. On reception of a Remote Frame with matching identifier, the TxRqst bit of this Mes-
sage Object is set (if RmtEn = 1).
MDir Mask Message Direction
0 The message direction bit (Dir) has no effect on the acceptance filtering.
1 The message direction bit (Dir) is used for acceptance filtering.
EoB End of Buffer
0 Message Object belongs to a FIFO Buffer and is not the last Message Object of that FIFO
Buffer.
1 Single Message Object or last Message Object of a FIFO Buffer.
NewDat New Data
0 No new data has been written into the data portion of this Message Object by the Message
Handler since last time this flag was cleared by the CPU.
1 The Message Handler or the CPU has written new data into the data portion of this Message
Object.