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5 message object in the message memory – FUJITSU MB91460 SERIES FR60 User Manual

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Chapter 34 CAN Controller

2.Register Description

2.5 Message Object in the Message Memory

There are 32 Message Objects (up to 128 depending on the implementation) 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.

Figure 2-4

gives an overview of the two structures of a Message Object.

Figure 2-4 Structure of a Message Object in the Message Memory

(Note)

The CPU must reset the MsgVal bit of all unused Message Objects during the initialization before it
resets bit Init in the CAN Control Register. This bit must also be reset before the identifier ID28-0,
the control bits Xtd, Dir, or the Data Length Code DLC3-0 are modified, or if the Message Object is
no longer required.

(Note)

If the UMask bit is set to one, the Message Object’s mask bits have to be programmed during
initialization of the Message Object before MsgVal is set to one.

Message Object

UMask

Msk28-0

MXtd

MDir

EoB

NewDat

MsgLst

RxIE

TxIE

IntPnd

RmtEn

TxRqst

MsgVal

ID28-0

Xtd

Dir

DLC3-0

Data0

Data1

Data2

Data3

Data4

Data5

Data6

Data7

MsgVal

Message Valid

0

The Message Object is ignored by the Message Handler.

1

The Message Object is configured and should be considered by the Message Handler.

UMask

Use Acceptance Mask

0

Mask ignored.

1

Use Mask (Msk28-0, MXtd, and MDir) for acceptance filtering.

ID28-0

Message Identifier

ID28 -

ID0

29-bit Identifier (“Extended Frame”).

ID28 -

ID18

11-bit Identifier (“Standard Frame”).

Msk28-0

Identifier Mask

0

The corresponding bit in the identifier of the message object cannot inhibit the match in the
acceptance filtering.

1

The corresponding identifier bit is used for acceptance filtering.

Xtd

Extended Identifier

0

The 11-bit (“standard”) Identifier will be used for this Message Object.