ST ST10F276E - Message Interface Register Sets; Table 61. IF1 and IF2 Message Interface Register Sets

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UM0404 CAN modules
BRP extension register
CAN1BRPER (EF0Ch) XBUS Reset Value: 0000h
CAN2BRPER (EE0Ch) XBUS Reset Value: 0000h
21.8.3 Message interface register sets
There are two sets of Interface Registers which are used to control the CPU access to the
Message RAM. The Interface Registers avoid conflicts between CPU access to the
Message RAM and CAN message reception and transmission by buffering the data to be
transferred. A complete Message Object (see Message object in the message memory) or
parts of the Message Object may be transferred between the Message RAM and the IFx
Message Buffer registers (see IFx message buffer registers) in one single transfer.
The function of the two interface register sets is identical (except for test mode Basic). They
can be used the way that one set of registers is used for data transfer to the Message RAM
while the other set of registers is used for the data transfer from the Message RAM,
allowing both processes to be interrupted by each other. Table 61 gives an overview of the
two Interface Register sets.
Each set of Interface Registers consists of Message Buffer Registers controlled by their own
Command Registers. The Command Mask Register specifies the direction of the data
transfer and which parts of a Message Object will be transferred. The Command Request
Register is used to select a Message Object in the Message RAM as target or source for the
transfer and to start the action specified in the Command Mask Register.
1514131211109876543210
------------ BRPE
RW
Bit Function
BRPE
Baud Rate Prescaler Extension
By programming BRPE (0h-Fh) the Baud Rate Prescaler can be extended to values
up to 1023. The actual interpretation by the hardware is that one more than the
value programmed by BRPE (MSBs) and BRP (LSBs) is used.
Table 61. IF1 and IF2 message interface register sets
Address IF1 register set Address IF2 register set
CAN Base + 0x10 IF1 Command Request CAN Base + 0x40 IF2 Command Request
CAN Base + 0x12 IF1 Command Mask CAN Base + 0x42 IF2 Command Mask
CAN Base + 0x14 IF1 Mask 1 CAN Base + 0x44 IF2 Mask 1
CAN Base + 0x16 IF1 Mask 2 CAN Base + 0x46 IF2 Mask 2
CAN Base + 0x18 IF1 Arbitration 1 CAN Base + 0x48 IF2 Arbitration 1
CAN Base + 0x1A IF1 Arbitration 2 CAN Base + 0x4A IF2 Arbitration 2
CAN Base + 0x1C IF1 Message Control CAN Base + 0x4C IF2 Message Control
CAN Base + 0x1E IF1 Data A 1 CAN Base + 0x4E IF2 Data A 1
CAN Base + 0x20 IF1 Data A 2 CAN Base + 0x50 IF2 Data A 2