Ifx Message Control Registers; Ifx Data A And Data B Registers; Message Object In The Message Memory - Bosch TTCAN User Manual

TTCAN

3.3.3.3 IFx Message Control Registers

IF1 Message Control Register
(addresses 0x1D & 0x1C)
IF2 Message Control Register
(addresses 0x4D & 0x4C)

3.3.3.4 IFx Data A and Data B Registers

The data bytes of CAN messages are stored in the IFx registers in the following order:
IF1 Message Data A1 (addresses 0x1F & 0x1E)
IF1 Message Data A2 (addresses 0x21 & 0x20)
IF1 Message Data B1 (addresses 0x23 & 0x22)
IF1 Message Data B2 (addresses 0x25 & 0x24)
IF2 Message Data A1 (addresses 0x4F & 0x4E)
IF2 Message Data A2 (addresses 0x51 & 0x50)
IF2 Message Data B1 (addresses 0x53 & 0x52)
IF2 Message Data B2 (addresses 0x55 & 0x54)
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.

3.3.4 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.
Figure 7 gives an overview of the two structure of a Message Object.
UMask Msk28-0 MXtd
MsgVal ID28-0
Figure 7: Structure of a Message Object in the Message Memory
MsgVal Message Valid
one
zero
Note : The CPU must reset the MsgVal bit of all unused Messages Objects during the initialization
before it resets bit Init in the CAN Control Register. This bit must also be reset before the iden-
tifier Id28-0, the control bits Xtd, Dir, or the Data Length Code DLC3-0 are modified, or if the
Messages Object is no longer required.
UMask Use Acceptance Mask
one
zero
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 .
BOSCH
15 14
NewDat MsgLst IntPnd UMask TxIE RxIE RmtEn TxRqst EoB MSC2-0 DLC3-0
NewDat MsgLst IntPnd UMask TxIE RxIE RmtEn TxRqst EoB MSC2-0 DLC3-0
rw rw
15 14 13 12 11 10
MDir EoB MSC2-0 NewDat MsgLst RxIE TxIE IntPnd RmtEn TxRqst
Xtd Dir DLC3-0 Data 0 Data 1 Data 2 Data 3 Data 4 Data 5 Data 6 Data 7
The Message Object is configured and should be considered by the Mes-
sage Handler.
The Message Object is ignored by the Message Handler.
Use Mask (Msk28-0, MXtd, and MDir) for acceptance filtering
Mask ignored.
User's Manual
13 12 11 10
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Data(1)
Data(3)
Data(5)
Data(7)
Data(1)
Data(3)
Data(5)
Data(7)
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Message Object
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9 8 7 6 5 4
Data(0)
Data(2)
Data(4)
Data(6)
Data(0)
Data(2)
Data(4)
Data(6)
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Revision 1.6
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11.11.02