
DocID13284 Rev 2
441/564
UM0404
CAN modules
21.8.4
Message handler registers
All Message Handler registers are read-only. Their contents (
TxRqst
,
NewDat
,
IntPnd
, and
MsgVal
bits of each Message Object and the Interrupt Identifier) is status information
provided by the Message Handler FSM.
Interrupt register
CAN1IR (EF08h)
XBUS
Reset Value: 0000h
CAN2IR (EE08h)
XBUS
Reset Value: 0000h
TxRqst
Transmit Request
’0’: This Message Object is not waiting for transmission.
’1’: The transmission of this Message Object is requested and is not yet done.
DLC(3:0)
Data Length Code
’0000’: Data Frame has 0 data byte.
’0001’: Data Frame has 1 data byte.
’1000’: Data Frame has 8 data bytes.
’1001’: Data Frame has 8 data bytes.
’1111’: Data Frame has 8 data bytes.
Note:
The Data Length Code of a Message Object must be defined the same as in
all the corresponding objects with the same identifier at other nodes. When the
Message Handler stores a data frame, it will write the DLC to the value given by the
received message.
Data 0
Data 1
Data 2
Data 3
Data 4
Data 5
Data 6
Data 7
1st data byte of a CAN Data Frame
2nd data byte of a CAN Data Frame
3rd data byte of a CAN Data Frame
4th data byte of a CAN Data Frame
5th data byte of a CAN Data Frame
6th data byte of a CAN Data Frame
7th data byte of a CAN Data Frame
8th data byte of a CAN Data Frame
Note:
Byte
Data 0
is the first data byte shifted into the shift register of the CAN Core
during a reception, byte
Data 7
is the last. 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
.
Bit
Function
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
IntId(15:0)
R